CN113646176A

CN113646176A - Ink set, image recording method, and image recorded matter

Info

Publication number: CN113646176A
Application number: CN202080025400.1A
Authority: CN
Inventors: 河合将晴; 篠原龙儿; 本乡悠史; 沟江大我
Original assignee: Fujifilm Corp
Current assignee: Fujifilm Corp
Priority date: 2019-03-28
Filing date: 2020-02-06
Publication date: 2021-11-12
Anticipated expiration: 2040-02-06
Also published as: US20220002570A1; EP3950355A4; JPWO2020195211A1; CN113646176B; WO2020195211A1; EP3950355A1

Abstract

The invention provides an ink set, an image recording method and an image recorded matter, wherein the ink set can record images with excellent hiding performance and adhesion to a non-permeable substrate. The ink set includes: a treatment liquid having a pH of 4.5 or less or 9.5 or more; and an ink containing a compound A which generates a gas in an environment having a pH of 4.5 or less or 9.5 or more, a resin, water, and a white pigment, wherein the pH is more than 4.5 and less than 9.5, and the ratio of the content mass of the white pigment to the content mass of the compound A in the ink is 1 or more and 160 or less.

Description

Ink set, image recording method, and image recorded matter

Technical Field

The present invention relates to an ink set, an image recording method and an image recorded matter.

Background

Conventionally, a white ink containing a white pigment is known.

For example, patent document 1 describes, as an aqueous white ink for inkjet having a low viscosity and excellent storage stability and pigment settling property, an aqueous white ink for inkjet containing titanium oxide as a pigment, at least titanium oxide, a pigment-dispersed resin, an organic solvent and water, wherein a resin obtained by copolymerizing at least an α -olefin, maleic acid and/or maleic anhydride is used as the pigment-dispersed resin.

Further, patent document 2 discloses, as an inkjet white ink which can perform recording with a sufficient whiteness and is further excellent in dispersion stability compared with the conventional one, an inkjet white ink which is characterized by substantially containing hollow particles composed only of a white metal oxide as a coloring material. Patent document 2 also discloses that at least one kind of white metal oxide is preferably selected from the group consisting of titanium oxide, zinc oxide, and antimony oxide.

Further, patent document 3 discloses an ink set which is capable of preventing bleeding between a plurality of inks and is less likely to cause clogging when a plurality of inks are stacked and recorded on a non-absorbent recording medium or a low-absorbent recording medium, the ink set including a reaction liquid containing a coagulant, a 1 st ink containing a coloring material, and a 2 nd ink containing a coloring material, and being used for recording on a non-absorbent recording medium or a low-absorbent recording medium, wherein the reaction liquid, the 1 st ink, and the 2 nd ink are sequentially stacked and applied on the recording medium. Patent document 3 discloses an embodiment in which at least one of the 1 st ink and the 2 nd ink is a color ink containing a color material or a black ink containing a black material, and the other of the 1 st ink and the 2 nd ink is a white ink containing a white pigment.

Prior art documents

Patent document

Patent document 1: japanese patent laid-open publication No. 2014-210837

Patent document 2: japanese patent laid-open publication No. 2013-23676

Patent document 3: japanese patent laid-open publication No. 2015-71738

Disclosure of Invention

Technical problem to be solved by the invention

An image recorded with an ink containing a white pigment is sometimes required to have low light transmittance (also referred to as "concealing property").

For example, when an image is recorded on the surface of a colored substrate, it is considered that the color of the substrate can be prevented from being visually recognized due to the image being transmitted because the hiding property of the image is high.

In the case where an image is recorded on the surface of a transparent base material, it is considered that since the concealing property of the image is high, the reduction in the visibility of the image due to the transmission of light through the transparent base material and the image can be suppressed.

Further, it is also known that the above-mentioned image recorded using an inkjet ink containing white inorganic pigment particles is further used as a base to be recorded on the lower side of other colored images.

By using an image having high concealing properties as the base, as described above, the color of the base material can be suppressed from being visible or light can be suppressed from transmitting through the base material and the image, and therefore, the visibility of the colored image can be improved.

According to the studies of the present inventors, it was found that when a treatment liquid is applied to a substrate and an ink is applied to the surface of the substrate to which the treatment liquid is applied to record an image, an image having excellent concealing properties can be recorded by using a treatment liquid having a pH of 4.5 or less or 9.5 or more as the treatment liquid and an ink containing a compound a generating a gas in an environment having a pH of 4.5 or less or 9.5 or more, a resin, water and a white pigment and having a pH of more than 4.5 and less than 9.5 as the ink.

However, according to further studies by the present inventors, it has been found that the adhesion of an image to a base material may be reduced in the image recorded as described above.

The present invention addresses the problem of providing an ink set capable of recording an image having excellent concealing properties and adhesion to a base material, an image recording method using the ink set, and an image recorded matter provided with an impermeable base material and an image having excellent concealing properties and adhesion to an impermeable base material.

Means for solving the technical problem

Specific means for solving the problems include the following means.

< 1 > an ink set comprising:

a treatment liquid having a pH of 4.5 or less or 9.5 or more;

An ink containing a compound A which generates a gas in an environment having a pH of 4.5 or less or 9.5 or more, a resin, water, and a white pigment, wherein the pH of the ink is more than 4.5 and less than 9.5;

the ratio of the mass content of the white pigment to the mass content of the compound A in the ink is 1 to 160.

< 2 > the ink set according to < 1 > wherein,

the absolute value of the difference between the pH of the treatment liquid and the pH of the ink is 3 or more.

< 3 > the ink set according to < 1 > or < 2 >, wherein,

the ratio of the mass content of the resin in the ink to the mass content of the compound A is 0.3 to 100.

< 4 > the ink set according to any one of < 1 > to < 3 >, wherein,

the ratio of the total mass content of the white pigment and the resin in the ink to the mass content of the compound A is 3 to 250.

< 5 > the ink set according to any one of < 1 > to < 4 >, wherein,

the compound A is urea.

< 6 > the ink set according to any one of < 1 > to < 5 >, wherein,

the content of the white pigment in the ink is 5 to 20% by mass based on the total amount of the ink.

< 7 > the ink set according to any one of < 1 > to < 6 >, wherein,

The white pigment comprises titanium dioxide particles.

< 8 > the ink set according to any one of < 1 > to < 7 >, wherein,

the ink is white ink.

< 9 > the ink set according to any one of < 1 > to < 8 >, wherein,

the content of the resin is 1 to 10% by mass based on the total amount of the ink,

the content of the compound A is 0.1 to 10% by mass based on the total amount of the ink.

< 10 > the ink set according to any one of < 1 > to < 9 >, wherein,

the resin contains resin particles.

< 11 > the ink set according to < 10 > wherein,

the glass transition temperature of the resin particles is 40 ℃ or higher.

< 12 > the ink set according to any one of < 1 > to < 11 >, wherein,

the ink is an inkjet ink.

< 13 > the ink set according to any one of < 1 > to < 12 >, wherein,

the treatment liquid contains at least one coagulant selected from the group consisting of organic acids, polyvalent metal compounds, metal complexes, and water-soluble cationic polymers.

< 14 > the ink set according to any one of < 1 > to < 13 > for image recording on an impermeable substrate.

< 15 > an image recording method using the ink set of any one of < 1 > to < 14 >, the image recording method having the steps of:

A step of applying a treatment liquid to an impermeable base material; and

and a step of applying ink to the surface of the non-permeable substrate to which the treatment liquid is applied, and recording an image.

< 16 > the image recording method according to < 15 > wherein,

the amount of the treatment liquid applied per unit area in the step of applying the treatment liquid was Xg/m²The ink supply per unit area in the step of recording an image is Yg/m²In the case of (2), the Y/X ratio is 3 to 25 inclusive.

< 17 > an image recorded matter, which comprises:

an impermeable substrate; and

an image disposed on the impermeable substrate and comprising a resin and a white pigment;

the void ratio in the image is 1% or more and 30% or less.

Effects of the invention

According to the present invention, there are provided an ink set capable of recording an image excellent in concealing properties and adhesion to a base material, an image recording method using the ink set, and an image recorded matter including an impermeable base material and an image excellent in concealing properties and adhesion to an impermeable base material.

Drawings

Fig. 1 is a schematic configuration diagram showing a configuration example of an ink jet recording apparatus used for performing image recording.

Fig. 2 is a black character image used for evaluation of concealment of images in the embodiment.

Detailed Description

In the present invention, the numerical range represented by the term "to" means a range in which the numerical values before and after the term "to" are included as the lower limit value and the upper limit value.

In the numerical ranges recited in the present invention in stages, the upper limit or the lower limit recited in a certain numerical range may be replaced with the upper limit or the lower limit recited in other numerical ranges recited in stages.

In the numerical ranges described in the present invention, the upper limit or the lower limit described in a certain numerical range may be replaced with the values shown in the examples.

In the present invention, the amount of each component in the composition refers to the total amount of a plurality of substances present in the composition, when a plurality of substances corresponding to each component are present in the composition, unless otherwise specified.

In the present invention, "recording of an image" means drawing an image on a substrate using an ink and a treatment liquid as needed and fixing the drawn image. The "image" may be an image recorded with ink, and includes characters, a solid film, and the like.

In the present invention, the term "step" includes not only an independent step but also a step that can achieve the intended purpose of the step even when it cannot be clearly distinguished from other steps.

In the present invention, "(meth) acrylic acid" means at least one of acrylic acid and methacrylic acid, and "(meth) acrylate" means at least one of acrylate and methacrylate.

[ ink set ]

The ink set of the present invention includes: a treatment liquid having a pH of 4.5 or less or 9.5 or more; and an ink containing a compound A which generates a gas in an environment having a pH of 4.5 or less or 9.5 or more, a resin, water and a white pigment, wherein the pH is more than 4.5 and less than 9.5, and the ratio of the mass content of the white pigment to the mass content of the compound A in the ink (hereinafter referred to as "mass content ratio [ white pigment/compound A ]) or simply as" white pigment/compound A ") is 1 or more and 160 or less.

According to the ink set of the present invention, an image having excellent concealing properties and adhesion to an impermeable substrate can be recorded.

The reason why this effect can be exhibited is presumed as follows.

According to the study of the present inventors, the following were found: when a treatment liquid is applied to an impermeable substrate, and an ink is applied to the surface of the impermeable substrate to which the treatment liquid is applied to record an image, the treatment liquid having a pH of 4.5 or less or 9.5 or more is used as the treatment liquid, and the ink containing a compound a which generates a gas in an environment having a pH of 4.5 or less or 9.5 or more, a resin, water, and a white pigment and having a pH of more than 4.5 and less than 9.5 is used as the ink, whereby an image having excellent concealing properties can be recorded. The reason is presumed to be as follows.

It is considered that, during the recording of an image, the treatment liquid contacts the compound a to generate a gas, and as a result, appropriate pores are formed in the recorded image. It is considered that the recorded image contains the above-mentioned pores in combination with the whiteness of the white pigment contained in the image, improving the concealment of the image. The effect of improving the concealing property is exhibited by the content mass ratio [ white pigment/compound A ] being 160 or less.

Further, according to further studies by the present inventors, it has been found that in the image recorded as described above, the adhesion of the image to the impermeable base material (hereinafter, also simply referred to as "adhesion") may be reduced.

This decrease in adhesion is considered to occur when the above-mentioned voids are too large in the image.

In the ink set of the present invention, the decrease in adhesion of an image is suppressed by the content mass ratio [ white pigment/compound a ] in the ink being 1 or more. The reason is considered to be because the porosity in the image can be suppressed.

In the ink set of the present invention, the treatment liquid having a pH of 4.5 or less or 9.5 or more (hereinafter, also referred to as "specific treatment liquid") is a treatment liquid satisfying any one of a pH of 4.5 or less and a pH of 9.5 or more.

The ink set of the present invention may include only 1 specific treatment liquid, or may include two or more specific treatment liquids.

For example, the ink set of the present invention may include 1 or more treatment liquids having a pH of 4.5 or less and 1 or more treatment liquids having a pH of 9.5 or less.

The ink set of the present invention may include only 1 kind of ink (hereinafter, also referred to as "specific ink") containing the compound a generating gas in an environment of pH 4.5 or less or 9.5 or more, the resin, the water, and the white pigment and having a pH of more than 4.5 and less than 9.5, or may include 2 or more kinds of ink (hereinafter, also referred to as "specific ink") containing the compound a generating gas in an environment of pH 4.5 or less or 9.5 or more, the resin, the water, and the white pigment and having a pH of more than 4.5 and less than 9.5.

The color of the specific ink is not particularly limited as long as it is a color exhibited by an ink containing a white pigment.

Examples of the color of the specific ink include white, gray, and a colored white (for example, light cyan, light magenta, light yellow, light blue, and pink).

Examples of the gray ink include specific inks containing a white pigment and a black coloring material.

Examples of colored inks with white color include specific inks containing a white pigment and a colored coloring material (e.g., cyan coloring material, magenta coloring material, and yellow coloring material).

The specific ink is preferably a white ink from the viewpoint of more effectively exhibiting the effect of improving the concealing property.

The white ink as used herein means an ink having a lightness of 9 or more as defined in JIS Z8721: 1993.

The ink set of the present invention may include a liquid other than the specific ink and the specific treatment liquid.

As the liquid other than the specific ink and the specific treatment liquid, ink other than the specific ink is preferable.

The ink other than the specific ink is preferably an ink other than a white ink (i.e., a color ink and/or a black ink), such as a cyan ink, a magenta ink, a yellow ink, or a black ink, and more preferably a color ink-jet ink and/or a black ink-jet ink.

The specific ink in the ink set of the present invention is not particularly limited, and is preferably an inkjet ink from the viewpoint of efficiency of image recording and the like.

That is, when the specific ink in the ink set of the present invention is an inkjet ink, it can be used in an inkjet recording apparatus. This enables efficient recording of a composite image in which a fine image formed by a color inkjet ink and/or a black inkjet ink and an image formed by the ink set of the present invention and having excellent concealing properties and adhesion are combined. The composite image can also be recorded using a single inkjet recording apparatus, in which case the composite image can be recorded more efficiently.

The inkjet ink preferably has a viscosity of 20cP or less.

The ink set of the present invention can be used for recording images on all substrates (i.e., recording media) such as paper substrates and resin substrates.

In general, in recording an image on an impermeable substrate (for example, a resin substrate), since ink hardly permeates into the substrate, it tends to be difficult to obtain adhesion between the image and the substrate as compared with the case of recording an image on a permeable substrate.

However, according to the ink set of the present invention capable of recording an image having excellent adhesion to a substrate, an image having excellent adhesion to an impermeable substrate can be obtained even when an impermeable substrate is used as a substrate.

Therefore, the ink set of the present invention is preferably used for recording an image on an impermeable substrate.

Preferred embodiments of the impermeable base material will be described later.

< specific ink >

The ink set of the present invention includes at least 1 specific ink (i.e., an ink containing a compound a that generates gas in an environment having a pH of 4.5 or less or 9.5 or more, a resin, water, and a white pigment and having a pH of more than 4.5 and less than 9.5).

(Compound A generating gas in an atmosphere having a pH of 4.5 or less or 9.5 or more)

The specific ink contains at least 1 compound A which generates gas in an environment having a pH of 4.5 or less or 9.5 or more.

Here, "gas is generated in an environment having a pH of 4.5 or less or 9.5 or more" means that at least one of gas generation in an environment having a pH of 4.5 or less and gas generation in an environment having a pH of 9.5 or more is satisfied.

The compound a is not particularly limited except for a compound that generates a gas in an environment having a pH of 4.5 or less or 9.5 or more, and examples thereof include urea, carbonates such as calcium carbonate, carboxylates such as sodium acetate, and ammonium salts such as ammonium chloride. Preferably, compound a does not generate gas in an environment having a pH of more than 4.5 and less than 9.5.

As compound a, urea is particularly preferable.

The content of the compound a is not particularly limited as long as the content mass ratio [ white pigment/compound a ] is in the range of 1 to 160, based on the total amount of the specific ink.

The content of the compound a is preferably 0.06 to 10% by mass, and more preferably 0.1 to 10% by mass, based on the total amount of the specific ink.

When the content of the compound a is 0.06% by mass or more based on the total amount of the specific ink, the concealing property of the image is further improved. From the viewpoint of further improving the concealing property of an image, the content of the compound a is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and further preferably 0.5% by mass or more, based on the total amount of the specific ink.

When the content of the compound a is 10% by mass or less based on the total amount of the specific ink, the adhesion of the image is further improved. From the viewpoint of further improving the adhesion of an image, the content of the compound a is preferably 4% by mass or less, more preferably 2% by mass or less, with respect to the total amount of the specific ink.

[ resin ]

The specific ink contains at least 1 resin.

The resin as used herein refers to all resin components contained in the specific ink.

Specific examples of the resin contained in the specific ink include resin particles that are particles made of a resin; a resin dispersant for coating at least a part of the pigment to disperse the pigment; and the like.

The resin contained in the specific ink preferably contains at least 1 type of resin particle.

When the resin contained in the specific ink contains resin particles, the adhesion of the image is further improved. Further, the ejection stability when the specific ink is used as an inkjet ink is also improved.

Resin particles-

The resin particles are preferably solid.

In the present invention, the solid shape is a term used as an antisense word to the hollow shape.

Specifically, the porosity of the resin particles is preferably less than 10%, more preferably 5% or less.

When the resin particles have voids, the porosity can be determined by the following formula. When the resin particles have no void, the void ratio is set to 0%.

Void ratio (%) (radius of pore of resin particle/radius of resin particle)³×100

And, when a plurality of pores are present in the resin particle instead of one,

void fraction (%) - [ Sigma (radius of pores in resin particles) ]³/(radius of resin particle (1/2 particle diameter))³X 100 was determined.

The radius of the resin particles and the radius of the pores of the resin particles are determined by observing the resin particles with a transmission electron microscope. The arithmetic average of the void ratios obtained for 100 resin particles was defined as the void ratio of the resin particles.

The glass transition temperature (Tg) of the resin particles is not particularly limited.

From the viewpoint of further improving the adhesion of an image, the glass transition temperature (Tg) of the resin particles is preferably 0 ℃ or higher, more preferably 40 ℃ or higher, even more preferably 80 ℃ or higher, even more preferably 120 ℃ or higher, and even more preferably 140 ℃ or higher.

The upper limit of the Tg of the resin particles is not particularly limited, but the Tg of the resin particles is preferably 300 ℃ or less, more preferably 200 ℃ or less, and further preferably 180 ℃ or less.

In the present invention, the measured glass transition temperature (Tg) obtained by actual measurement is used as the Tg.

Specifically, the Tg measured is a value measured under ordinary measurement conditions using a Differential Scanning Calorimeter (DSC) EXSTAR6220 manufactured by Hitachi High-Tech Science Corporation. However, when it is difficult to measure the Tg by decomposition of the resin, the Tg calculated by the following calculation formula is used. Calculation of Tg was calculated from the following formula (1).

1/Tg＝Σ(Xi/Tgi)…(1)

Here, it is assumed that the resin to be calculated is obtained by copolymerizing n monomer components of i 1 to n. Xi is the weight fraction of the ith monomer (Σ Xi ═ 1), and Tgi is the glass transition temperature (absolute temperature) of the homopolymer of the ith monomer. Where Σ takes the sum of 1 to n. In addition, the value of the homopolymer glass transition temperature (Tgi) of each monomer was a value of Polymer Handbook (3rd Edition) (j. brandrup, e.h. immergut (Wiley-Interscience, 1989)). The value of the homopolymer glass transition temperature of the monomer not described in the above document is obtained as a measurement Tg by the above measurement method after the preparation of the homopolymer of the monomer. In this case, the influence of the weight average molecular weight on the Tg of the polymer can be ignored by setting the weight average molecular weight of the homopolymer to 10,000 or more.

The glass transition temperature of the resin particles can be appropriately controlled by a commonly used method. For example, the glass transition temperature of the resin particles can be controlled within a desired range by appropriately selecting the kind or the composition ratio of the monomer (polymerizable compound) constituting the resin particles, the molecular weight of the resin constituting the resin particles, and the like.

Examples of the resin in the resin particles include acrylic resins, epoxy resins, polyether resins, polyamide resins, unsaturated polyester resins, phenol resins, silicone resins, fluorine resins, polyethylene resins (e.g., vinyl chloride, vinyl acetate, polyvinyl alcohol, polyvinyl butyral, etc.), alkyd resins, polyester resins (e.g., phthalic resins, etc.), amino materials (e.g., cyanuric acid resins, melamine formaldehyde resins, amino alkyd co-condensation resins, urea resins, etc.), and the like.

The resin particles are preferably particles of an acrylic resin, a polyether resin, a polyester resin, or a polyolefin resin, and more preferably particles of an acrylic resin.

In the present invention, the acrylic resin refers to a resin containing a structural unit derived from (meth) acrylic acid or a (meth) acrylate compound. The acrylic resin may contain a structural unit other than a structural unit derived from (meth) acrylic acid or a (meth) acrylate compound.

The resin forming the resin particles may be a copolymer containing two or more kinds of structural units constituting the resins exemplified above, or may be a mixture of two or more kinds of resins. The resin particles themselves may be not only resin particles composed of a mixture of two or more resins, but also composite resin particles in which two or more resins are laminated, for example, as in a core/shell structure.

The resin particles are preferably resin particles obtained by a phase inversion emulsification method, and more preferably particles of a self-dispersible resin (self-dispersible resin particles).

The self-dispersible resin is a water-insoluble resin which can be dispersed in an aqueous medium by a functional group (particularly, an acidic group such as a carboxyl group or a salt thereof) of the resin itself when the resin is dispersed by a phase inversion emulsification method in the absence of a surfactant.

Here, the dispersion state includes both an emulsified state (emulsion) in which the water-insoluble resin is dispersed in a liquid state in an aqueous medium and a dispersed state (suspension) in which the water-insoluble resin is dispersed in a solid state in an aqueous medium.

Also, "water-insoluble" means that the amount of dissolution is less than 5.0 parts by mass (preferably less than 1.0 part by mass) with respect to 100 parts by mass (25 ℃) of water.

Examples of the phase inversion emulsification method include the following methods: after dissolving or dispersing the resin in a solvent (e.g., a water-soluble solvent), the resin is directly put into water without adding a surfactant, and stirred and mixed in a state where a salt-forming group (e.g., an acidic group such as a carboxyl group) of the resin is neutralized, and the solvent is removed, thereby obtaining an aqueous dispersion in an emulsified or dispersed state.

The self-dispersible resin particles can be selected from the self-dispersible resin particles described in paragraphs 0090 to 0121 of Japanese patent application laid-open No. 2010-64480 or paragraphs 0130 to 0167 of Japanese patent application laid-open No. 2011-068085.

As the self-dispersible resin particles, self-dispersible resin particles having a carboxyl group are preferable.

A more preferred form of the self-dispersible resin particle having a carboxyl group is a form composed of a resin containing a structural unit derived from an unsaturated carboxylic acid (preferably (meth) acrylic acid).

A more preferred embodiment of the self-dispersible resin particle having a carboxyl group is an embodiment composed of a resin containing:

a structural unit having an alicyclic group;

a structural unit having an alkyl group; and

structural units derived from unsaturated carboxylic acids, preferably (meth) acrylic acid.

The content (total content when two or more kinds are present) of the structural unit having an alicyclic group in the resin is preferably 3 to 95% by mass, more preferably 5 to 75% by mass, and still more preferably 10 to 50% by mass, based on the total amount of the resin.

The content of the structural unit having an alkyl group in the resin (total content when two or more kinds are present) is preferably 5 to 90% by mass, more preferably 10 to 85% by mass, further preferably 20 to 80% by mass, further preferably 30 to 75% by mass, further preferably 40 to 75% by mass, based on the total amount of the resin.

The content (total content when two or more species are present) of the structural unit derived from an unsaturated carboxylic acid (preferably (meth) acrylic acid) in the resin is preferably 2 to 30% by mass, more preferably 5 to 20% by mass, and still more preferably 5 to 15% by mass, relative to the total amount of the resin.

Further, as the form of the self-dispersible resin particle having a carboxyl group, a form in which the structural unit having an alicyclic group is changed to a structural unit having an aromatic group or a form in which the structural unit having an aromatic group is contained in addition to the structural unit having an alicyclic group is also preferable in the above "further preferable form of the self-dispersible resin particle having a carboxyl group".

In any of the embodiments, the total content of the structural unit having an alicyclic group and the structural unit having an aromatic group is preferably 3 to 95% by mass, more preferably 5 to 75% by mass, and still more preferably 10 to 50% by mass, based on the total amount of the resin.

The structural unit having an alicyclic group is preferably a structural unit derived from an alicyclic (meth) acrylate.

Examples of the alicyclic (meth) acrylate include monocyclic (meth) acrylates, 2-cyclic (meth) acrylates, and 3-cyclic (meth) acrylates.

Examples of the monocyclic (meth) acrylate include cycloalkyl (meth) acrylates having a cycloalkyl group of 3 to 10 carbon atoms, such as cyclopropyl (meth) acrylate, cyclohexyl (meth) acrylate, cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, cycloheptyl (meth) acrylate, cyclooctyl (meth) acrylate, cyclononyl (meth) acrylate, and cyclodecyl (meth) acrylate.

Examples of the 2-ring type (meth) acrylate include isobornyl (meth) acrylate, norbornyl (meth) acrylate, and the like.

Examples of the 3-ring type (meth) acrylate include adamantyl (meth) acrylate, dicyclopentyl (meth) acrylate, and dicyclopentenyloxyethyl (meth) acrylate.

They can be used alone or in combination of two or more.

Among these, from the viewpoints of fixing property, blocking resistance and dispersion stability of the self-dispersible resin particles, 2-ring type (meth) acrylate or 3-or more-ring type polycyclic (meth) acrylate is preferable, and isobornyl (meth) acrylate, adamantyl (meth) acrylate or dicyclopentanyl (meth) acrylate is more preferable.

The structural unit having an aromatic group is preferably a structural unit derived from a monomer having an aromatic group.

Examples of the aromatic group-containing monomer include aromatic group-containing (meth) acrylate monomers (e.g., phenoxyethyl (meth) acrylate, benzyl (meth) acrylate, phenyl (meth) acrylate, etc.), styrene compounds, and the like.

Among them, from the viewpoint of balance between hydrophilicity and hydrophobicity of the resin chain and ink fixability, a (meth) acrylate monomer containing an aromatic group is preferable, phenoxyethyl (meth) acrylate, benzyl (meth) acrylate, or phenyl (meth) acrylate is more preferable, and phenoxyethyl (meth) acrylate or benzyl (meth) acrylate is further preferable.

The structural unit having an alkyl group is preferably a structural unit derived from a monomer containing an alkyl group.

Examples of the alkyl group-containing monomer include alkyl (meth) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, hexyl (meth) acrylate, and ethylhexyl (meth) acrylate; ethylenically unsaturated monomers having a hydroxyl group such as hydroxymethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, hydroxypentyl (meth) acrylate, and hydroxyhexyl (meth) acrylate; dialkylaminoalkyl (meth) acrylates such as dimethylaminoethyl (meth) acrylate; n-hydroxyalkyl (meth) acrylamides such as N-hydroxymethyl (meth) acrylamide, N-hydroxyethyl (meth) acrylamide, and N-hydroxybutyl (meth) acrylamide; and (meth) acrylamides such as N-alkoxyalkyl (meth) acrylamide and the like, such as N-methoxymethyl (meth) acrylamide, N-ethoxymethyl (meth) acrylamide, N- (N, i) butoxymethyl (meth) acrylamide, N-methoxyethyl (meth) acrylamide, N-ethoxyethyl (meth) acrylamide, and N- (N, i) butoxyethyl (meth) acrylamide and the like.

Among these, an alkyl (meth) acrylate is preferable, an alkyl (meth) acrylate in which the alkyl group has 1 to 4 carbon atoms is more preferable, methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, or butyl (meth) acrylate is further preferable, and methyl (meth) acrylate is further preferable.

The weight average molecular weight of the resin constituting the resin particles (preferably self-dispersible resin particles. the same applies hereinafter) is preferably 3000 to 20 ten thousand, more preferably 5000 to 15 ten thousand, and still more preferably 10000 to 10 ten thousand.

When the weight average molecular weight is 3000 or more, the amount of the water-soluble component can be effectively suppressed. Further, the self-dispersion stability can be improved by setting the weight average molecular weight to 20 ten thousand or less.

The weight average molecular weight of the resin constituting the resin particles is a value measured by Gel Permeation Chromatography (GPC).

In the measurement based on Gel Permeation Chromatography (GPC), HLC (registered trademark) -8020GPC (Tosoh Corporation) was used as a measurement device, 3 TSKgel (registered trademark) Super multi HZ-H (4.6mmID × 15cm, Tosoh Corporation) was used as a column, and THF (tetrahydrofuran) was used as an eluent. The measurement conditions were 0.45 mass% for the sample concentration, 0.35ml/min for the flow rate, 10 μ l for the sample injection amount, 40 ℃ for the measurement temperature, and a differential Refractive Index (RI) detector.

Calibration curve is obtained from Tosoh Corporation "Standard specimen TSK Standard, polystyrene": 8 samples of "F-40", "F-20", "F-4", "F-1", "A-5000", "A-2500", "A-1000" and "n-propylbenzene" were prepared.

From the viewpoint of self-dispersibility and the rate of aggregation upon contact with a treatment liquid, the resin constituting the resin particles is preferably a resin having an acid value of 100mgKOH/g or less, more preferably a resin having an acid value of 25mgKOH/g to 100 mgKOH/g.

The volume average particle diameter of the resin particles is preferably in the range of 1nm to 200nm, more preferably in the range of 1nm to 150nm, still more preferably in the range of 1nm to 100nm, and particularly preferably in the range of 1nm to 10 nm. When the volume average particle diameter is 1nm or more, the production suitability is improved. Further, when the volume average particle diameter is 200nm or less, the storage stability is improved. The particle size distribution of the resin particles a is not particularly limited, and may be a particle size distribution having a broad particle size distribution or a particle size distribution having a monodisperse particle size distribution.

The volume average particle diameter of the resin particles is measured by a particle size distribution measuring apparatus using light scattering (for example, microtrack UPA (registered trademark) EX150 manufactured by Nikkiso co., ltd.).

From the viewpoint of improving the concealing property, the refractive index of the resin particles is preferably 1.0 to 1.7.

One kind of the resin particles may be used alone, or two or more kinds may be used in combination.

The content (total content in the case of two or more types) of the resin particles (preferably the self-dispersible resin particles) in the ink is not particularly limited, but is preferably 0.5 to 11% by mass, more preferably 0.5 to 9% by mass, even more preferably 2 to 9% by mass, and even more preferably 2 to 7% by mass, relative to the total amount of the ink.

When the content is 0.5% by mass or more, the adhesion of the image is further improved.

When the content is 11% by mass or less, the dispersion stability of the ink can be further improved. Therefore, for example, when the ink is used as an inkjet ink, the ejection stability from the inkjet head (hereinafter also simply referred to as "ejection stability") can be further improved.

Specific examples of the resin particles are given below, but the present invention is not limited to these. In addition, the mass ratio of the copolymerization components is shown in parentheses.

Methyl methacrylate/isobornyl methacrylate/methacrylic acid/sodium methacrylate copolymer (70/20/5/5), Tg: 150 ℃ C

Joncryl (registered trademark) JDX-C3080 (JHNSON POLYMER Co., Ltd.), Tg: 130 deg.C

Toray Pearl (registered trademark) EP, Toray INDUSTRIES, inc, Tg: 190 deg.C

Toray Pearl (registered trademark) PES, Toray INDUSTRIES, inc, Tg: 225 deg.C

Resin dispersants-

The specific ink may contain, as a resin, a resin dispersant for covering at least a part of the pigment to disperse the pigment.

The pigment referred to herein is a pigment contained in a specific ink represented by a white pigment described later.

As the resin dispersant, an acrylic resin is preferable.

As the resin dispersant, for example, the dispersants described in paragraphs 0080 to 0096 of Japanese patent laid-open publication No. 2016-145312 are preferable.

The content of the dispersant is preferably 3 to 20% by mass, more preferably 4 to 18% by mass, and still more preferably 5 to 15% by mass, based on the total content of the pigments contained in the specific ink.

The content of the dispersant is preferably 0.1 to 2.4% by mass, more preferably 0.5 to 2.0% by mass, and still more preferably 0.8 to 1.5% by mass, based on the total amount (z% by mass) of the specific ink.

Preferred content of resin

The content of the resin (for example, the resin particles and the resin dispersant) in the specific ink (for example, the total content of the resin particles and the resin dispersant) is preferably 1 to 12% by mass, more preferably 1 to 10% by mass, even more preferably 3 to 10% by mass, and even more preferably 3 to 8% by mass, based on the total amount of the specific ink.

The ratio of the mass content of the resin (for example, resin particles and resin dispersant) to the mass content of the compound a in the specific ink (hereinafter also referred to as "mass content ratio [ resin/compound a ]" or "resin whole/compound a") is preferably 0.1 to 120, more preferably 0.2 to 100, and still more preferably 0.3 to 100.

When the content mass ratio [ resin/compound A ] is 0.1 or more, the adhesion of the image is further improved. From the viewpoint of further improving the adhesion of an image, the content mass ratio [ resin/compound a ] is more preferably 0.2 or more, still more preferably 0.3 or more, still more preferably 0.5 or more, still more preferably 1 or more, still more preferably 2 or more, and still more preferably 3 or more.

When the content mass ratio [ resin/compound A ] is 120 or less, the concealing property of the image is further improved. From the viewpoint of further improving the concealment of an image, the content ratio [ resin/compound a ] by mass is more preferably 100 or less, still more preferably 50 or less, and still more preferably 20 or less.

(white pigment)

The specific ink contains at least 1 kind of white pigment.

The white pigment is not particularly limited, and known white pigments can be used, and examples thereof include titanium dioxide particles (TiO)₂) Inorganic pigment particles such as zinc oxide particles, barium sulfate particles, silica particles, alumina particles, magnesium oxide particles, calcium silicate particles, calcium carbonate particles, kaolin particles, talc particles, and colloidal silica particles. Further, as the white pigment, hollow resin particles may be mentioned.

The white pigment particularly preferably contains titanium dioxide particles from the viewpoint of concealing the image.

Since the titanium dioxide particles have a large refractive index, when the white pigment contains titanium dioxide particles, the concealing property of the image is further improved.

The titanium dioxide particles include anatase type titanium dioxide particles, rutile type titanium dioxide particles, brookite type titanium dioxide particles, and the like, but rutile type titanium dioxide particles are preferable from the viewpoint of refractive index. Further, since rutile titanium dioxide particles have a lower photocatalytic action than anatase titanium dioxide particles and brookite titanium dioxide particles, they have an advantage of having a small influence on a resin, a resin base material, and the like in a specific ink.

In the case where the white pigment contains titanium dioxide particles, the white pigment may contain a white pigment (e.g., inorganic pigment particles) other than the titanium dioxide particles.

When the white pigment contains titanium dioxide particles, the proportion of the titanium dioxide particles in the total amount of the white pigment is preferably 20% by mass or more, more preferably 50% by mass or more, and still more preferably 80% by mass or more. The upper limit of the proportion of the titanium dioxide particles in the total amount of the white pigment is not particularly limited, and may be 100 mass% or less.

The average primary particle size of the white pigment is preferably 100nm or more, more preferably 150nm or more, and still more preferably 200nm or more, from the viewpoint of further improving the concealing property of an image.

The average primary particle diameter of the white pigment is preferably 400nm or less, and more preferably 300nm or less, from the viewpoint of dispersion stability of the ink (for example, ejection stability when the ink is used as an inkjet ink).

The average primary particle diameter of the white pigment in the present invention is a value measured by a Transmission Electron Microscope (TEM). A transmission electron microscope 1200EX manufactured by JEOL co., ltd. can be used in the measurement.

Specifically, an ink diluted 1,000 times was dropped onto Cu200 mesh (manufactured by JEOL co., ltd.) to which a carbon film was attached and dried, and then the equivalent circle diameters of 300 independent particles which were not overlapped were measured from an image magnified 10 ten thousand times by TEM, and the measured values were averaged to obtain an average particle diameter.

In addition, the refractive index of the white pigment is preferably 2.0 or more from the viewpoint of concealing an image.

In the present invention, the "refractive index" means a value measured by spectroscopic ellipsometry at a temperature of 23 ℃ under visible light having a wavelength of 550nm, unless otherwise specified.

The content of the white pigment in the specific ink is preferably 1 to 20% by mass, more preferably 3 to 20% by mass, even more preferably 5 to 20% by mass, even more preferably 6 to 20% by mass, and even more preferably 7 to 15% by mass, based on the total amount of the specific ink.

When the content of the white pigment in the specific ink is 1% by mass or more based on the total amount of the specific ink, the concealing property of the image is further improved.

When the content of the white pigment in the specific ink is 20% by mass or less with respect to the total amount of the specific ink, the adhesion of the image is further improved.

As described above, the specific ink contains the white pigment in a mass ratio [ white pigment/compound a ] (i.e., a ratio of the mass of the white pigment contained to the mass of the compound a) of 1 to 160.

From the viewpoint of further improving the adhesion of the image, the content mass ratio [ white pigment/compound a ] is preferably 2 or more, more preferably 3 or more.

From the viewpoint of further improving the concealing property of an image, the content ratio by mass [ white pigment/compound a ] is more preferably 100 or less, still more preferably 50 or less, and still more preferably 20 or less.

The ratio of the total content mass of the white pigment and the resin in the specific ink to the content mass of the compound a (hereinafter also referred to as "content mass ratio [ (white pigment and resin)/compound a ]" or "(white pigment + resin whole)/compound a") is preferably 3 or more and 250 or less.

When the content mass ratio [ (white pigment and resin)/compound A ] is 3 or more, the adhesion of the image is further improved. From the viewpoint of further improving the adhesion of the image, the content mass ratio [ (white pigment and resin)/compound a ] is more preferably 6 or more, and still more preferably 7 or more.

When the content mass ratio [ (white pigment and resin)/compound a ] is 250 or less, the concealing property of the image is further improved. From the viewpoint of further improving the concealing property of an image, the content mass ratio [ (white pigment and resin)/compound a ] is more preferably 240 or less, still more preferably 100 or less, still more preferably 50 or less, and still more preferably 30 or less.

(other coloring materials)

The specific ink may further contain a coloring material other than the white pigment.

Examples of the other coloring material include organic pigment particles and inorganic pigment particles, and preferable examples thereof include pigment particles described in paragraphs 0029 to 0041 of Japanese patent application laid-open No. 2011-94112.

The proportion of the white pigment in the whole coloring material contained in the specific ink is preferably 50% by mass or more, more preferably 80% by mass or more, and still more preferably 90% by mass or more.

The proportion of the white pigment in the entire coloring material contained in the specific ink may be 100% by mass.

(Water)

The specific ink contains water.

The content of water is preferably 30% by mass or more, more preferably 40% by mass or more, and still more preferably 50% by mass or more, based on the total amount of the specific ink.

The upper limit of the amount of water also depends on the amount of other ingredients. The upper limit of the water content relative to the total amount of the specific ink is, for example, 90 mass% or 80 mass%.

(Water-soluble solvent)

The specific ink preferably contains at least 1 kind of water-soluble solvent.

This can suppress drying of the specific ink or can obtain a wetting effect of the specific ink.

The water-soluble solvent that can be contained in the specific ink can also be used, for example, as an anti-drying agent that prevents clogging from occurring due to formation of aggregates caused by adhesion and drying of the specific ink at the ink ejection port of the ejection nozzle of the inkjet head.

In the present invention, "water-soluble" refers to a property of dissolving 1g or more of water per 100g of water at 25 ℃.

The "water-soluble" in the present invention is preferably 5g or more (more preferably 10g or more) per 100g of water at 25 ℃.

From the viewpoint of suppression of drying and wetting, a water-soluble solvent having a lower vapor pressure than water (hereinafter, also referred to as "anti-drying agent") is preferable as the water-soluble solvent contained in the specific ink.

The boiling point of the water-soluble solvent at one atmospheric pressure (1013.25hPa) is preferably 80 to 300 ℃, more preferably 120 to 250 ℃.

Specific examples of the anti-drying agent include polyhydric alcohols typified by ethylene glycol, propylene glycol, diethylene glycol, polyethylene glycol, thiodiethylene glycol, dithiodiethylene glycol, 2-methyl-1, 3-propanediol, 1,2, 6-hexanetriol, acetylene glycol derivatives, glycerin, trimethylolpropane, and the like.

Among them, polyhydric alcohols such as glycerin and diethylene glycol are preferable as the anti-drying agent.

The anti-drying agent can be used singly or in combination of two or more. The content of the anti-drying agent is preferably 5 to 50% by mass, more preferably 10 to 40% by mass, and still more preferably 10 to 40% by mass, based on the total amount of the specific ink.

The water-soluble solvent can be used for adjusting the viscosity of the ink, in addition to the above.

Specific examples of the water-soluble solvent that can be used for adjusting the viscosity include alcohols (e.g., methanol, ethanol, propanol, isopropanol, butanol, isobutanol, sec-butanol, tert-butanol, pentanol, hexanol, cyclohexanol, benzyl alcohol), polyols (e.g., ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexylene glycol, pentanediol, glycerol, hexanetriol, thiodiglycol), glycol derivatives (e.g., ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, triethylene glycol monomethyl ether, ethylene glycol diacetate, ethylene glycol monomethyl ether acetate, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, ethylene glycol monophenyl ether), amines (e.g., ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenetriamine, triethylenetetramine, polyethyleneimine, tetramethylpropylenediamine) and other polar solvents (e.g., formamide, N-dimethylformamide, N-dimethylacetamide, dimethyl sulfoxide, sulfolane, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, 2-oxazolidinone, 1, 3-dimethyl-2-imidazolidinone, acetonitrile, acetone).

In this case, one kind of the water-soluble solvent may be used alone, and two or more kinds may be used in combination.

The content of the water-soluble solvent is preferably 5 to 50% by mass, more preferably 10 to 40% by mass, and still more preferably 10 to 40% by mass, based on the total amount of the specific ink.

(other additives)

The specific ink may contain other components in addition to the above components.

Examples of the other components include known additives such as colloidal silica, inorganic salts, discoloration inhibitors, emulsion stabilizers, permeation enhancers, ultraviolet absorbers, preservatives, antifungal agents, pH adjusters, surface tension adjusters, antifoaming agents, viscosity adjusters, dispersion stabilizers, rust inhibitors, chelating agents, and water-soluble polymer compounds.

(pH of specific ink)

The pH of the specific ink exceeds 4.5 and is less than 9.5.

This can suppress the generation of gas derived from the compound a (i.e., the compound a that generates gas in an environment where the pH is 4.5 or less or 9.5 or more) in the specific ink before the contact with the treatment liquid.

The pH of the specific ink is preferably 5 or more and 9 or less.

In the present invention, the pH refers to the pH measured using a pH meter at a measurement temperature of 25 ℃.

(viscosity of specific ink)

The viscosity of the specific ink is preferably 1 to 30 mPas, more preferably 1.5 to 20 mPas.

In the present invention, the viscosity means that the shear rate is 1,400s at a measurement temperature of 23 ℃ C^-1The value measured by a viscometer under the conditions of (1).

As the viscometer, for example, a TV-20 type viscometer (TOKI SANGYO co., ltd.

(surface tension of specific ink)

The surface tension of the specific ink is preferably 20 to 60mN/m, more preferably 20 to 45mN/m, and still more preferably 25 to 40 mN/m.

In the present invention, the surface tension is a value measured by a plate method at 25 ℃.

As a measuring apparatus for measuring the Surface tension, for example, an Automatic Surface tensometer CBVP-Z (Kyowa Interface Science Co., Ltd.) can be used.

< specific treatment liquid >

The ink set of the present invention includes at least 1 specific treatment liquid (i.e., a treatment liquid having a pH of 4.5 or less or 9.5 or more).

As described above, by recording an image by bringing a specific ink and a specific treatment liquid into contact with each other using the ink set of the present invention, a gas is generated from the compound a (i.e., the compound a that generates a gas in an environment having a pH of 4.5 or less or 9.5 or more) in the process of recording an image. Thereby, an image having pores is recorded. The pores in the image contribute to the effect of improving the concealment of the image.

From the viewpoint of further improving the concealing property of an image, the absolute value of the difference between the pH of the specific treatment liquid and the pH of the specific ink (hereinafter also referred to as "absolute value of pH difference") is preferably 2.5 or more, and more preferably 3 or more.

The upper limit of the absolute value of the pH difference is preferably 7.5, more preferably 7, still more preferably 6, and yet more preferably 5.

The pH of the specific treatment liquid may be 4.5 or less or 9.5 or more by including a component (flocculant, etc.) described later in the specific treatment liquid, by including a pH adjuster in the specific treatment liquid, or by including a pH adjuster and a component (flocculant, etc.) described later in the specific treatment liquid.

The pH adjuster is not particularly limited, and examples thereof include inorganic acids (e.g., hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, etc.), inorganic bases (e.g., alkali metal hydroxides, alkaline earth metal hydroxides, ammonia, ammonium salts, etc.), organic bases [ e.g., alkylammonium hydroxides (e.g., tetraalkylammonium hydroxides such as tetramethylammonium hydroxide), amine compounds (e.g., alkanolamines such as triethanolamine), etc. ].

(coagulant)

The specific treatment liquid preferably contains at least one coagulant selected from the group consisting of organic acids, polyvalent metal compounds, metal complexes, and water-soluble cationic polymers.

The aggregating agent has a function of aggregating components (for example, a white pigment and resin particles in the case of containing resin particles) in the specific ink. Therefore, when the specific treatment liquid contains the coagulant, the concealing property of the image is further improved.

Organic acids-

Examples of the organic acid include organic compounds having an acidic group.

Examples of the acidic group include a phosphoric acid group, a phosphonic acid group, a phosphinic acid group, a sulfuric acid group, a sulfonic acid group, a sulfinic acid group, and a carboxyl group.

The acidic group is preferably a phosphoric group or a carboxyl group, and more preferably a carboxyl group, from the viewpoint of the coagulation rate of the ink.

In addition, the acidic group is preferably at least partially dissociated in the treatment solution.

As the organic compound having a carboxyl group, polyacrylic acid, acetic acid, formic acid, benzoic acid, glycolic acid, malonic acid, malic acid (preferably DL-malic acid), maleic acid, succinic acid, glutaric acid, fumaric acid, citric acid, tartaric acid, phthalic acid, 4-methylphthalic acid, lactic acid, pyrrolidone carboxylic acid, pyrone carboxylic acid, pyrrole carboxylic acid, furan carboxylic acid, pyridine carboxylic acid, coumaric acid, thiophene carboxylic acid, nicotinic acid, and the like are preferable. One of these compounds may be used, or two or more of them may be used in combination.

As the organic compound having a carboxyl group, a carboxylic acid having a valence of 2 or more (hereinafter, also referred to as a polycarboxylic acid) is preferable from the viewpoint of the coagulation rate of the ink.

The polycarboxylic acid is more preferably malonic acid, malic acid, maleic acid, succinic acid, glutaric acid, fumaric acid, tartaric acid, 4-methylphthalic acid, or citric acid, and further preferably malonic acid, malic acid, tartaric acid, or citric acid.

The organic acid preferably has a low pKa (e.g., 1.0 to 5.0).

In this way, the surface charge of particles such as pigments and polymer particles in the ink, which are dispersed and stabilized in a weakly acidic functional group such as a carboxyl group, is reduced by contacting the particles with an organic acidic compound having a lower pKa, and the dispersion stability can be lowered.

The organic acid is preferably an acidic substance having a low pKa, a high solubility in water, and a valence of 2 or more, and more preferably a valence of 2 or 3 having a high buffering capacity in a pH region lower than the pKa of a functional group (for example, a carboxyl group or the like) for stabilizing dispersion of particles in the ink.

Polyvalent metal compounds

Examples of the polyvalent metal compound include salts of alkaline earth metals of group 2 of the periodic table (for example, magnesium and calcium), transition metals of group 3 of the periodic table (for example, lanthanum), cations derived from group 13 of the periodic table (for example, aluminum), and lanthanides (for example, neodymium).

The salt of these metals is preferably a salt of the above-mentioned organic acid, a nitrate, a chloride or a thiocyanate.

Among them, calcium salts or magnesium salts of organic acids (formic acid, acetic acid, benzoic acid salts, etc.), calcium salts or magnesium salts of nitric acid, calcium chloride, magnesium chloride, or thiocyanic acid are preferable.

The polyvalent metal compound is preferably at least partially dissociated into a polyvalent metal ion and a counter ion in the treatment liquid.

Metal complexes

As the metal complex, a metal complex containing at least one selected from the group consisting of zirconium, aluminum, and titanium as a metal element is preferable.

As the metal complex, a metal complex containing at least one selected from the group consisting of acetate, acetylacetonate, methyl acetoacetate, ethyl acetoacetate, octyleneglycolate (octyleneglycollate), butoxyacetylacetonate (butoxyacetyl acetate), lactate, ammonium lactate, and triethanolamine ester (triethanol amide) as a ligand is preferable.

Various metal complexes are commercially available, and in the present invention, commercially available metal complexes can be used. Furthermore, various organic ligands, in particular, various polydentate ligands capable of forming metal chelate catalysts are commercially available. Therefore, a metal complex prepared by combining a commercially available organic ligand and a metal can be used.

Examples of the metal complex include zirconium tetraacetylacetonate (e.g., "Orgatix ZC-150" manufactured by Matsumoto Fine Chemical co., ltd.), zirconium monoacetylacetonate (e.g., "Orgatix ZC-540" manufactured by Matsumoto Fine Chemical co., ltd.), zirconium bisacetylacetonate (e.g., "Orgatix ZC-550" manufactured by ltd.), zirconium monoacetylacetate (e.g., "Orgatix ZC-560" manufactured by Matsumoto Fine Chemical co., ltd.), zirconium acetate (e.g., "Orgatix ZC-560" manufactured by Matsumoto Fine Chemical co., ltd.), titanium diisopropoxide bis (acetylacetonate) (e.g., "Orgatix TC-100" manufactured by Matsumoto Fine co., ltd.), titanium tetraacetylacetonate (e.g., "Orgatix TC-115" manufactured by Matsumoto co., ltd.), "dioctyloxyacetate (e.g.," Orgatix TC-401 "manufactured by Matsumoto Fine co., "Orgatix TC-200" manufactured by ltd., Matsumoto Fine Chemical co., ltd., diisopropoxytitanium bis (ethylacetoacetate) (e.g., "Orgatix TC-750" manufactured by Matsumoto Fine Chemical co., ltd, "Orgatix TC-300" manufactured by ltd., Matsumoto Fine Chemical co., ltd.), titanium lactate (e.g., "Orgatix TC-310, 315" manufactured by ltd., Matsumoto Fine Chemical co., ltd., triethanolamine titanium (e.g., "Orgatix TC-400" manufactured by ltd., Matsumoto Fine Chemical co., ltd.), zirconium chloride compound (e.g., "Orgatix ZC-126" manufactured by ltd., ltd.).

Among these, preferred are titanium ammonium lactate (e.g., "Orgatix TC-300" manufactured by Matsumoto Fine Chemical co., ltd.), titanium lactate (e.g., "Orgatix TC-310, 315" manufactured by Matsumoto Fine Chemical co., ltd.), titanium triethanolamine (e.g., "Orgatix TC-400" manufactured by Matsumoto Fine Chemical co., ltd.), zirconium chloride compounds (e.g., "Orgatix ZC-126" manufactured by Matsumoto Fine Chemical co., ltd.).

Water-soluble cationic polymers

Examples of the water-soluble cationic polymer include polyallylamine, polyallylamine derivatives, poly-2-hydroxypropyldimethylammonium chloride, and poly (diallyldimethylammonium chloride).

As the water-soluble cationic polymer, there can be appropriately mentioned the descriptions of known documents such as Japanese patent application laid-open No. 2011-042150 (especially, paragraphs 0156), Japanese patent application laid-open No. 2007-98610 (especially, paragraphs 0096 to 0108), and the like.

Commercially available products of water-soluble cationic polymers include SHAROL (registered trademark) DC-303P, SHAROL DC-902P (DKS Co. Ltd. above), cation Master (registered trademark) PD-7, cation Master PD-30 (Yokkaichi Chemical Company Limited) and UNISENCE FPA100L (SENKA CORPORATION).

The content of the flocculant is not particularly limited, and is preferably 0.1 to 40% by mass, more preferably 0.1 to 30% by mass, still more preferably 1 to 20% by mass, and particularly preferably 1 to 10% by mass, based on the total amount of the specific treatment liquid.

The coagulant preferably contains an organic acid from the viewpoint of further improving the concealing property of an image.

The preferable range of the content of the organic acid with respect to the entire specific treatment liquid in the case where the flocculant contains an organic acid is also the same as the above-mentioned content of the flocculant with respect to the total amount of the specific treatment liquid.

When the flocculant contains an organic acid, the organic acid accounts for preferably 50 to 100% by mass, more preferably 80 to 100% by mass, and still more preferably 90 to 100% by mass of the total amount of the flocculant.

(Water)

The specific treatment liquid preferably contains water.

The content of water is preferably 50% by mass or more, and more preferably 60% by mass or more, based on the total amount of the specific treatment liquid.

The upper limit of the amount of water also depends on the amount of other ingredients. Examples of the upper limit of the water content relative to the total amount of the specific treatment liquid include 90 mass% and 80 mass%.

(resin particles)

The specific treatment liquid may contain at least 1 kind of resin particles.

When the specific treatment liquid contains resin particles, the adhesion of the image is further improved.

From the viewpoint of further improving the adhesion of the obtained image, the Tg of the resin particles is preferably 100 ℃ or lower, more preferably 75 ℃ or lower.

The resin contained in the resin particles is not particularly limited, and examples thereof include a polyurethane resin, a polyamide resin, a polyurea resin, a polycarbonate resin, a polyolefin resin, a polystyrene resin, a polyester resin, and an acrylic resin.

The resin particles preferably contain a polyester resin and/or an acrylic resin, and more preferably contain a polyester resin.

Alicyclic or aromatic ring structures-

The resin contained in the resin particle preferably has an alicyclic structure or an aromatic ring structure in the structure, and more preferably has an aromatic ring structure.

The alicyclic structure is preferably an alicyclic hydrocarbon structure having 5 to 10 carbon atoms, and is preferably a cyclohexane ring structure, a dicyclopentenyl ring (dicyclopentenyl ring) structure, or an adamantane ring structure.

The aromatic ring structure is preferably a naphthalene ring or a benzene ring, and more preferably a benzene ring.

The amount of the alicyclic structure or aromatic ring structure is, for example, preferably 0.01 to 1.5mol, and more preferably 0.1 to 1mol per 100g of the resin contained in the resin particles.

-ionic groups-

The resin particles are preferably water-dispersible. From this viewpoint, the resin contained in the resin particles preferably has an ionic group in the structure.

The ionic group may be an anionic group or a cationic group, but an anionic group is preferable from the viewpoint of easy introduction.

The anionic group is not particularly limited, but is preferably a carboxyl group or a sulfo group, and more preferably a sulfo group.

The amount of the ionic group is, for example, preferably 0.001 to 1.0mol, and more preferably 0.01 to 0.5mol per 100g of the resin contained in the resin particle.

The content of the resin particles is not particularly limited.

The content of the resin particles is preferably 0.5 to 30% by mass, more preferably 1 to 20% by mass, and particularly preferably 1 to 15% by mass, based on the total amount of the specific treatment liquid.

(Water-soluble solvent)

The specific treatment liquid preferably contains at least one water-soluble solvent.

As the water-soluble solvent, a known water-soluble solvent can be used without particular limitation.

Examples of the water-soluble solvent include polyhydric alcohols such as glycerin, 1,2, 6-hexanetriol, trimethylolpropane, alkanediol (e.g., ethylene glycol, propylene glycol (1, 2-propanediol), 1, 3-propanediol, 1, 3-butanediol, 1, 4-butanediol, 2-butene-1, 4-diol, 2-ethyl-1, 3-hexanediol, 2-methyl-2, 4-pentanediol, 1, 2-octanediol, 1, 2-hexanediol, 1, 2-pentanediol, 4-methyl-1, 2-pentanediol, etc.), polyalkylene glycol (e.g., diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, dipropylene glycol, polyoxyethylene polyoxypropylene glycol, etc.); polyalkylene glycol ethers (e.g., diethylene glycol monoalkyl ether, triethylene glycol monoalkyl ether, tripropylene glycol monoalkyl ether, polyoxypropylene glycerol ether, etc.); saccharides, sugar alcohols, hyaluronic acids, alkyl alcohols having 1 to 4 carbon atoms, glycol ethers, 2-pyrrolidone, and N-methyl-2-pyrrolidone described in section 0116 of Japanese patent application laid-open No. 2011-42150.

Among them, from the viewpoint of suppressing transfer of the component, a polyol or polyol ether is preferable, and an alkanediol, a polyalkylene glycol, or a polyalkylene glycol ether is more preferable.

(surfactant)

Certain treatment fluids may comprise at least one surfactant.

Surfactants can be used as surface tension modifiers or defoamers. Examples of the surface tension adjusting agent and the defoaming agent include nonionic surfactants, cationic surfactants, anionic surfactants, and betaine surfactants. Among them, from the viewpoint of the coagulation rate of the specific ink, a nonionic surfactant or an anionic surfactant is preferable.

As the surfactant, there may be mentioned those exemplified as surfactants in Japanese patent application laid-open No. Sho 59-157636, pages 37 to 38 and Research Disclosure No.308119 (1989). Further, fluorine-based (fluoroalkyl-based) surfactants and silicone-based surfactants described in each of Japanese patent application laid-open Nos. 2003-322926, 2004-325707, and 2004-309806 can be cited.

When the specific treatment liquid contains a surfactant, the content of the surfactant in the specific treatment liquid is not particularly limited, but the surface tension of the specific treatment liquid is preferably 50mN/m or less, more preferably 20mN/m to 50mN/m, and still more preferably 30mN/m to 45 mN/m.

For example, when the specific treatment liquid contains a surfactant as an antifoaming agent, the content of the surfactant as the antifoaming agent is preferably 0.0001 to 1% by mass, and more preferably 0.001 to 0.1% by mass, based on the total amount of the specific treatment liquid.

(other Components)

The specific treatment liquid may contain other components than those described above as necessary.

Examples of the other components that can be contained in the specific treatment liquid include known additives such as a solid wetting agent, colloidal silica, an inorganic salt, a discoloration inhibitor, an emulsion stabilizer, a penetration enhancer, an ultraviolet absorber, a preservative, a fungicide, a pH adjuster, a viscosity adjuster, a rust inhibitor, a chelating agent, and a water-soluble polymer compound other than a water-soluble cationic polymer (for example, the water-soluble polymer compound described in paragraphs 0026 to 0080 of jp 2013-001854 a).

(pH of specific treatment liquid)

The pH of the specific treatment liquid is 4.5 or less or 9.5 or more, as described above.

The pH of the specific treatment liquid having a pH of 4.5 or less is preferably 1.0 or more and 4.5 or less, more preferably 2.0 or more and 4.5 or less, and further preferably 3.0 or more and 4.5 or less.

The pH of the specific treatment liquid having a pH of 9.5 or more is preferably 9.5 or more and 14.0 or less, more preferably 9.5 or more and 13.0 or less, further preferably 9.5 or more and 12.0 or less, and further preferably 9.5 or more and 11.0 or less.

The conditions for measuring the pH of the specific treatment liquid are the same as those for measuring the pH of the specific ink described above.

(viscosity of specific treatment liquid)

The viscosity of the specific treatment liquid is preferably in the range of 0.5 mPas to 10 mPas, more preferably in the range of 1 mPas to 5 mPas.

The conditions for measuring the viscosity of the specific treatment liquid are the same as those for measuring the viscosity of the specific ink described above.

(surface tension of specific treatment liquid)

The surface tension of the specific treatment liquid is preferably 60mN/m or less, more preferably 20mN/m to 50mN/m, and still more preferably 30mN/m to 45 mN/m.

The conditions for measuring the surface tension of the specific treatment liquid are the same as those for measuring the surface tension of the specific ink described above.

[ image recording method ]

The image recording method of the present invention is an image recording method used for the ink set of the present invention described above.

The image recording method of the present invention includes the steps of: a step of applying the treatment liquid to the substrate (hereinafter also referred to as "treatment liquid applying step"); and

And a step of applying the specific ink to the surface of the substrate to which the specific treatment liquid is applied and recording an image (hereinafter also referred to as "image recording step").

The image recording method of the present invention may include other processes as necessary.

According to the image recording method of the present invention, an image having excellent concealing properties and adhesion can be recorded.

The reason why these effects can be obtained is as described above.

< substrate >

The substrate in the image recording method of the present invention is not particularly limited, and examples thereof include paper, coated paper, resin substrates, metals, ceramics, glass, textile substrates, and the like.

According to the image recording method of the present invention, since an image having excellent concealing properties and adhesion can be obtained, an impermeable substrate is preferable as the substrate in the image recording method of the present invention.

In the present invention, the term "non-permeable substrate" means a substrate which absorbs little or no water, and specifically means a substrate having an absorption amount of water of 0.3g/m²The following groupA material is provided.

The water absorption (g/m) of the substrate was measured in the following manner²)。

Water was brought into contact with a 100mm × 100mm area in the surface of the substrate (i.e., the surface on which an image was to be recorded), and the substrate was held at 25 ℃ for 1 minute in this state. The mass of water (absorption amount (g)) absorbed by the retention for 1 minute was obtained, and the obtained absorption amount (g) was converted into an absorption amount per unit area (g/m) ²)。

The non-permeable substrate is not particularly limited, but a resin substrate is preferable.

The resin substrate is not particularly limited, and examples thereof include substrates made of thermoplastic resins.

Examples of the resin substrate include a substrate obtained by molding a thermoplastic resin into a sheet shape.

The resin substrate preferably comprises polypropylene, polyethylene terephthalate, nylon, polyethylene, or polyimide.

The resin substrate may be a transparent resin substrate or a colored resin substrate, and at least a part of the resin substrate may be subjected to a metal vapor deposition treatment or the like.

In the present invention, "transparent" means that the minimum transmittance at 23 ℃ at a wavelength of 400nm to 700nm is 80% or more (preferably 90% or more, more preferably 95% or more). The minimum transmittance is measured on a 1nm scale using a spectrophotometer (for example, spectrophotometer UV-2100 manufactured by SHIMADZU CORPORATION).

The shape of the resin base material is not particularly limited, but a sheet-like resin base material is preferable, and a sheet-like resin base material that can be formed into a roll by winding is more preferable from the viewpoint of productivity of the image recorded matter.

The thickness of the resin substrate is preferably 10 to 200. mu.m, more preferably 10 to 100. mu.m.

< treatment liquid imparting step >

The image recording method of the present invention includes a treatment liquid application step (i.e., a step of applying a treatment liquid to a substrate).

The treatment liquid can be applied to the substrate by applying a known method such as a coating method, an ink jet method, or a dipping method.

Examples of the coating method include known coating methods using a bar coater (e.g., a wire bar coater), an extrusion die coater, an air knife coater, a blade coater, a bar coater, a blade coater, an extrusion coater, a reverse roll coater, a gravure coater, a flexographic coater, and the like.

The details of the ink jet method are the same as those of the ink jet method applicable to an image recording step described later.

As the imparted mass per unit area of the treating liquid (Xg/m described later)²) Preferably 0.1g/m²～10g/m²More preferably 0.5g/m²～6.0g/m²More preferably 0.8g/m²～2.0g/m²More preferably 1.2g/m²～1.6g/m²。

In the treatment liquid application step, the treatment liquid may be dried by heating after the application of the treatment liquid and between the image recording steps (i.e., before the application of the ink).

Examples of the means for heating and drying the treatment liquid include known heating means such as a heater, known air blowing means such as a dryer, and a combination thereof.

Examples of the method for heating and drying the treatment liquid include the following: a method of applying heat from the side of the substrate opposite to the surface to which the treatment liquid is applied, using a heater or the like; a method of blowing warm air or hot air to the surface of the substrate to which the treatment liquid is applied; a method of applying heat from the side of the substrate to which the treatment liquid is applied or the side of the substrate opposite to the side to which the treatment liquid is applied, by an infrared heater; a method of combining a plurality of these methods, and the like.

The heating temperature in the heat drying is preferably 35 ℃ or higher, more preferably 40 ℃ or higher.

The upper limit of the heating temperature is not particularly limited, but is preferably 100 ℃, more preferably 90 ℃, and still more preferably 70 ℃.

The time for the heat drying is not particularly limited, but is preferably 0.5 to 60 seconds, more preferably 0.5 to 20 seconds, and particularly preferably 0.5 to 10 seconds.

< image recording Process >

The image recording method of the present invention includes an image recording step (i.e., a step of applying a specific ink to the surface of the substrate to which the specific treatment liquid is applied to record an image).

The specific ink can be applied by a known method such as an application method, an ink jet method, or a dipping method, but is preferably applied by an ink jet method from the viewpoint of recording a fine image.

As the ink jet method, a known ink jet method can be applied.

The ejection method of the specific ink in the ink jet method is not particularly limited, and may be a known method such as a charge control method of ejecting ink by utilizing an electrostatic induction force; a drop-on-demand method (pressure pulse method) using the vibration pressure of the piezoelectric element; an acoustic inkjet method in which an electric signal is changed into an acoustic beam, the acoustic beam is irradiated to ink, and the ink is ejected by radiation pressure; and a thermal ink Jet (registered trademark) system in which ink is heated to form bubbles and the generated pressure is used.

As the ink jet method, among the methods described in japanese patent application laid-open No. 54-59936, an ink jet method can be effectively used, in which the ink subjected to thermal energy undergoes a rapid volume change, and the ink is ejected from the nozzles by the urging force generated by the state change.

The ink jet method can be applied to the methods described in paragraphs 0093 to 0105 of Japanese patent application laid-open No. 2003-306623.

The application of the specific ink by the ink jet method is performed by ejecting the specific ink from a nozzle of an ink jet head.

As a method of the ink jet head, there is a Shuttle (Shuttle) method of performing recording while scanning a short Serial head (Serial head) in the width direction of the base material; and a Line head (Line head) type in which recording elements are arranged corresponding to the entire area of one side of the substrate.

In the line system, the entire surface of the base material can be subjected to image recording by scanning the base material in a direction intersecting the arrangement direction of the recording elements. In the line system, a transport system such as a Carriage (Carriage) for scanning a short-sized head in the shuttle system is not required. In addition, in the line type system, as compared with the reciprocating system, the movement of the carriage and the complicated scanning control of the base material are not required, and only the base material is moved. Therefore, according to the line system, the image recording speed can be increased compared to the shuttle system.

The amount of the specific ink droplets discharged from the nozzles of the ink jet head is preferably 1pL (picoliter) to 10pL, and more preferably 1.5pL to 6pL, from the viewpoint of obtaining a high-definition image.

Further, it is also effective to discharge droplets in combination of different amounts from the viewpoint of improving the unevenness of images and the connection of continuous gradation.

The inkjet head may have a liquid repellent film on a surface (ink ejection surface) from which the specific ink is ejected. Examples of the lyophobic film include lyophobic films described in paragraphs 0178 to 0184 of Japanese patent laid-open publication No. 2016-.

As the given mass of the specific ink per unit area in the image recording step (Yg/m described later) ²) Preferably 4.5g/m²～25g/m²More preferably 5.5g/m²～20g/m²More preferably 9g/m²～12g/m²。

In the image recording step, the specific ink to be applied may be dried by heating.

Examples of the means for heating and drying include known heating means such as a heater, known air blowing means such as a dryer, and a combination thereof.

Examples of the method for performing the heat drying of the specific ink include the following:

a method of applying heat from the side of the substrate opposite to the side to which the specific ink is applied, with a heater or the like;

a method of blowing warm air or hot air to the surface of the substrate to which the specific ink is applied;

a method of applying heat from the side of the substrate to which the specific ink is applied or the side of the substrate opposite to the side to which the specific ink is applied, by an infrared heater; a method of combining a plurality of these methods, and the like.

The heating temperature at the time of heating and drying of the specific ink is preferably 55 ℃ or higher, more preferably 60 ℃ or higher, and particularly preferably 65 ℃ or higher.

The upper limit of the heating temperature of the specific ink is not particularly limited, and as the upper limit, 100 ℃ is preferable, and 90 ℃ is more preferable.

The time for heating and drying the specific ink is not particularly limited, but is preferably 3 seconds to 60 seconds, more preferably 5 seconds to 60 seconds, and particularly preferably 10 seconds to 45 seconds.

In the image recording step, the substrate to which the treatment liquid is applied may be heated before the application of the specific ink.

The heating temperature may be appropriately set according to the type of the substrate and the composition of the specific ink, and is preferably 20 to 50 ℃, more preferably 25 to 40 ℃.

In addition, when the treatment liquid is heated and dried in the treatment liquid applying step, the heating for heating and drying the treatment liquid may be performed as the heating of the substrate before the ink is applied.

In the image recording method of the present invention, the amount of the specific treatment liquid applied per unit area in the treatment liquid applying step is Xg/m²The amount of the specific ink applied per unit area in the image recording step is Yg/m²In the case of (3), the Y/X ratio is preferably 2 or more and 28 or less, more preferably 3 or more and 25 or less, further preferably 4.5 or more and 20 or less, further preferably 6 or more and 15 or less, further preferably 6 or more and 10 or less.

< other working procedures >

The image recording method of the present invention may further include other processes.

Examples of the other step include a step of applying a black or color ink (hereinafter, also referred to as "coloring ink") to the substrate and recording a black or color image (hereinafter, also referred to as "colored image").

The coloring ink may be provided in the ink set of the present invention, or may be prepared separately from the ink set of the present invention.

The step of recording the colored image may be performed before the image recording step (preferably, before the image recording step and after the treatment liquid applying step).

In this case, an image based on a specific ink (for example, a white solid image) is recorded on a colored image (for example, a pattern image such as a character or a figure) recorded by the step of recording the colored image. Thereby, a colored image can be recorded between the substrate and an image based on a specific ink (for example, a white solid image).

When recording such an image, a transparent substrate is preferably used. Thus, when viewed from the image non-recording surface (i.e., the surface on which no image is recorded) side of the base material, a colored image (e.g., a pattern image such as a character or a figure) in which an image based on a specific ink (e.g., a white solid image) is a background can be visually recognized through the base material. On the other hand, when viewed from the image recording surface (i.e., the surface on which an image is recorded) side of the substrate, the colored image and the substrate are hidden by the image based on the specific ink, and it is difficult to visually recognize the colored image and the substrate.

The step of recording the colored image may be performed after the image recording step.

A colored image (e.g., a pattern image of characters, graphics, etc.) can be recorded on a specific ink-based image (e.g., a white solid image). In this case, when viewed from the image recording surface side of the base material, a colored image (for example, a pattern image such as a character or a figure) in which an image based on a specific ink (for example, a white solid image) is a base can be visually recognized. On the other hand, when the colored image is viewed from the image non-recording surface side of the substrate, the colored image is hidden by the image formed with the specific ink, and thus the colored image is not easily visible.

The method of applying the coloring ink is not particularly limited, and examples thereof include the same methods as the ink jet method described in the description of the image recording step.

The coloring ink is not particularly limited, and known water-based inks and the like can be used.

The coloring ink may be provided in 1 type alone or 2 or more types. Multicolor images can be recorded by imparting 2 or more types of coloring inks.

[ image record ]

The image recorded matter of the present invention is an image recorded matter that includes a base material (preferably, a non-permeable base material, the same applies hereinafter) and an image that is disposed on the base material and that includes a resin and a white pigment, and that has a void ratio in the image of 1% or more and 30% or less.

The image recorded matter of the present invention is excellent in image concealment and adhesion.

The void ratio of 1% or more contributes to the effect of concealing.

The porosity of 30% or less contributes to the effect of adhesion.

From the viewpoint of further improving the concealing property and the adhesion of an image, the void ratio in the image is preferably 5% or more and 25% or less, and more preferably 10% or more and 15% or less.

In the present invention, the void ratio in the image means a value measured as follows.

A cross section of the image was observed with a Scanning Electron Microscope (SEM), and an SEM image (magnification 25,000 times) was obtained.

Based on the SEM image, the void ratio in the image was calculated by the following equation.

Void ratio (%) in the image ═ ((total area of pores)/(total area of images containing pores)) × 100

The SEM image was obtained, for example, using a Thermo Fisher Scientific K.K. manufacturing Helios 400S FIB-SEM complex machine.

The image recorded matter of the present invention can be preferably produced by the above-described image recording method of the present invention.

In this case, the resin in the image is derived from at least the resin in the specific ink (i.e., the whole resin). When the treatment liquid contains resin particles, the resin in the image is derived from the resin in the specific ink and the resin particles in the treatment liquid.

The white pigment in the image is derived from the white pigment in the particular ink.

The pores in the image are derived from the gas generated by the contact of the compound a in the specific ink with the treatment liquid.

The preferred embodiment of the base material in the image recorded matter of the present invention can be referred to as appropriate in the part of the image recording method.

Regarding the components in the image recorded matter of the present invention, the portions of the ink set can be appropriately referred to.

The image recorded matter of the present invention includes not only an image containing a resin and a white pigment but also the colored image described above.

[ laminate ]

The image recorded matter of the present invention may further include a laminate substrate disposed on the image disposed on the substrate.

Hereinafter, the image recorded matter of this embodiment is referred to as a laminate.

The laminate is obtained by laminating a laminating substrate on the side of the image-recorded matter on which the image is disposed, for example.

The laminate substrate may be directly laminated on the side of the image-recorded matter on which the image is disposed, or may be laminated via another layer (e.g., an adhesive layer).

The lamination when the laminating base material is directly laminated on the side of the image-recorded matter on which the image is disposed can be performed by a known method such as thermocompression bonding or thermal bonding.

The lamination when the laminating base material is laminated to the image-disposed side of the image-recorded matter via the adhesive layer can be carried out, for example, by applying an adhesive to the image-disposed side of the image-recorded matter, placing the laminating base material thereon, and then bonding the image-recorded matter and the laminating base material.

The lamination when the image-recorded matter is laminated on the side on which the image is disposed via the adhesive layer can also be performed by a method such as extrusion lamination (i.e., Sandwich lamination).

The adhesive layer in the embodiment of laminating the image-recorded matter on the side on which the image is disposed via the adhesive layer preferably contains an isocyanate compound.

When the adhesive layer contains an isocyanate compound, the adhesion between the adhesive layer and the image is further improved, and therefore the lamination strength can be further improved.

As the substrate for lamination, a resin substrate is preferable.

The shape of the resin base material is not particularly limited, but a sheet-like resin base material is preferable.

[ image recording apparatus ]

The image recording method of the present invention can be implemented using, for example, a known inkjet recording apparatus.

Examples of the known ink jet recording apparatus include those described in japanese patent application laid-open nos. 2010-83021, 2009-234221, and 10-175315.

An example of an image recording apparatus that can be used in the image recording method of the present invention will be described below with reference to fig. 1.

The image recording apparatus shown in fig. 1 includes a treatment liquid applying mechanism for applying a treatment liquid and an image recording mechanism for performing an ink jet method.

Here, fig. 1 is a schematic configuration diagram showing a configuration example of the image recording apparatus.

As shown in fig. 1, the image recording apparatus includes, in order from a supply portion 11 of the substrate toward a conveying direction of the substrate (a direction of an arrow in the figure): a treatment liquid applying section 12 which includes an anilox roller 20 and an application roller 22 in contact therewith as a roller material to which a treatment liquid is applied; a treatment liquid drying area 13 provided with a heating mechanism (not shown) for drying the applied treatment liquid; an ink ejecting section 14 that ejects various inks; and an ink drying region 15 for drying the ejected ink.

The base material supply unit 11 in the image recording apparatus may be a supply unit that supplies a base material from a case in which the base material is loaded, or may be a supply unit that supplies a base material from a roll in which the base material is wound in a roll shape.

The substrate is transported from the supply unit 11 to the treatment liquid applying unit 12, the treatment liquid drying region 13, the ink discharge unit 14, and the ink drying region 15 in this order by the

transport rollers

41, 42, 43, 44, 45, and 46, and is collected in the collecting unit 16.

In the accumulating section 16, the base material can be wound into a roll shape.

As the transport of the substrate, a roller transport system using a roller-shaped member, a conveyor belt transport system, a Stage transport system using a Stage (Stage), or the like can be used in addition to the transport roller shown in fig. 1.

At least one of the plurality of

conveyance rollers

41, 42, 43, 44, 45, and 46 can be a drive roller to which power of a motor (not shown) is transmitted.

The substrate is conveyed at a predetermined conveying speed in a predetermined direction by rotating a drive roller rotated by a motor at a constant speed.

The treatment liquid applying unit 12 is provided with an anilox roller 20 disposed by immersing a part of a reservoir storing a specific treatment liquid, and an application roller 22 in contact with the anilox roller 20. The anilox roller 20 is a roller material for supplying a predetermined amount of a specific treatment liquid to an application roller 22 disposed opposite to an image recording surface of a base material. A specific treatment liquid is uniformly applied to the substrate by supplying an appropriate amount of the application roller 22 from the anilox roller 20.

The coating roller 22 is configured to be capable of conveying the substrate in a pair with the counter roller 24, and the substrate is conveyed to the treatment liquid drying area 13 through a gap between the coating roller 22 and the counter roller 24.

A treatment liquid drying region 13 is disposed downstream of the treatment liquid applying section 12 in the substrate conveying direction.

The treatment liquid drying region 13 can be configured by using a known heating mechanism such as a heater, an air blowing mechanism using air blowing such as a dryer or an air knife, or a combination thereof.

Examples of the heating mechanism include: a method of providing a heat generating body such as a heater on the side of the substrate opposite to the treatment liquid applying surface (i.e., image recording surface) (e.g., below a conveying mechanism on which the substrate is placed and conveyed when the substrate is automatically conveyed), a method of blowing warm air or hot air to the treatment liquid applying surface (i.e., image recording surface) of the substrate, and the like; a heating method using an infrared heater, and the like. The heating mechanism may combine a plurality of the above methods.

In the treatment liquid drying region 13, the solvent may be removed from the specific treatment liquid using a solvent removal roller or the like.

The ink ejection portion 14 is disposed on the downstream side of the treatment liquid drying region 13 in the conveyance direction of the substrate.

Recording heads (ink ejecting heads) 30K, 30C, 30M, 30Y, 30A, and 30W connected to ink storage portions for storing inks of respective colors of black (K), cyan (C), magenta (M), yellow (Y), spot color ink (a), and white (W) are disposed in the ink ejecting portion 14. Inks containing a colorant and water corresponding to the respective colors are stored in ink storage portions, not shown, and are supplied to the ink discharge heads 30K, 30C, 30M, 30Y, 30A, and 30W as necessary when recording an image.

Since the specific ink in the present invention is preferably white ink, the ink discharge head 30W is preferably an ink discharge head used for discharging the specific ink.

In fig. 1, the ink discharge head 30W is disposed on the downstream side (the most downstream side) of the ink discharge head 30A, but may be disposed on the upstream side of the ink discharge head 30K, or the like.

Examples of the spot color ink (a) include orange, green, violet, light cyan, and light magenta inks.

The ink discharge head 30A can be omitted in the image recording apparatus to which the image recording method of the present invention is applied. In addition to the ink discharge head 30A, other spot color ink discharge heads may be provided.

In fig. 1, for convenience, the position of the ink discharge head 30A is described on the downstream side of the yellow (Y) ink discharge head 30Y in the conveyance direction of the substrate, but the position is not particularly limited and may be appropriately set in consideration of the lightness of the spot color ink.

For example, a mode in which the ink discharge head 30A is positioned between the yellow ink discharge head 30Y and the magenta ink discharge head 30M, a mode in which the ink discharge head 30A is positioned between the magenta ink discharge head 30M and the cyan ink discharge head 30C, and the like can be considered.

The ink discharge heads 30K, 30C, 30M, 30Y, 30A, and 30W discharge ink corresponding to an image from discharge nozzles disposed to face the image recording surface of the base material. Thereby, the inks of the respective colors are applied to the image recording surface of the base material to record a color image.

The ink discharge heads 30K, 30C, 30M, 30Y, 30A, and 30W are all full-line heads in which a plurality of discharge ports (nozzles) are arranged over the maximum recording width of an image recorded on the surface of the base material. This enables high-speed image recording on the base material, compared to a serial head that performs recording while reciprocally scanning a short reciprocal head in the width direction of the base material (direction orthogonal to the conveyance direction of the base material).

In the present invention, either a serial type recording or a relatively high-speed recording system, for example, a single pass (single pass) system recording in which 1 line is formed by 1 scan, can be adopted, and according to the image recording method of the present invention, a high-quality image with high reproducibility can be obtained even in the single pass system.

Here, the ink discharge heads 30K, 30C, 30M, 30Y, 30A, and 30W all have the same configuration.

The amount of the treatment liquid and the amount of the ink are preferably adjusted as necessary. For example, the amount of the treatment liquid to be applied may be changed in order to adjust the physical properties such as viscoelasticity of an aggregate formed by mixing the treatment liquid and the ink, depending on the substrate.

The ink drying region 15 is disposed on the downstream side of the ink ejecting section 14 in the conveyance direction of the substrate.

The ink drying area 15 can be configured in the same manner as the treatment liquid drying area 13.

The image recording apparatus may further include a heating mechanism for performing a heating process on the base material on the transport path from the supply unit 11 to the accumulating unit 16.

For example, by disposing a heating mechanism at a desired position such as upstream of the treatment liquid drying region 13 or between the ink discharge portion 14 and the ink drying region 15, the temperature of the base material is raised to a desired temperature, and drying of the treatment liquid, drying of the ink, fixing of the ink, and the like can be efficiently performed.

Further, since the surface temperature of the substrate changes depending on the type (material, thickness, etc.) of the substrate, the ambient temperature, and the like, it is preferable that the image recording apparatus includes a heating control unit having a measuring unit that measures the surface temperature of the substrate, a heating control unit that controls the heating conditions, and a control unit that feeds back the value of the surface temperature of the substrate measured by the measuring unit to the heating control unit.

The image recording apparatus is provided with a heating control mechanism, and can supply the processing liquid, ink, and the like while controlling the temperature of the substrate.

As the measuring portion for measuring the surface temperature of the substrate, a contact or non-contact thermometer is preferable.

Examples

Examples of the present invention will be described below, but the present invention is not limited to the following examples.

Hereinafter, "part(s)" and "%" are based on mass unless otherwise specified.

[ example 1 ]

An ink and a treatment liquid were prepared, and an ink set including the ink and the treatment liquid was prepared.

The details are shown below.

< preparation of ink >

(Synthesis of resin particle P1)

Resin particles P1, one of the components in the ink, were synthesized. The details are shown below.

A three-necked flask equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen inlet was charged with methyl ethyl ketone (281g), and the temperature was raised to 85 ℃. While maintaining the reflux state, a mixed solution of methyl methacrylate (208g), isobornyl methacrylate (60g), methacrylic acid (30g), methyl ethyl ketone (66g) and "V-601" (manufactured by FUJIFILM Wako Pure Chemical Corporation) (0.66g) was uniformly dropped in the reaction vessel so that the dropping was completed within 3 hours. After completion of the dropwise addition, stirring was carried out for 1 hour, and (1) a solution composed of "V-601" (0.66g) and methyl ethyl ketone (3.5g) was added and stirred for 2 hours. Subsequently, the step (1) was repeated 4 times, and a solution of "V-601" (0.66g) and methyl ethyl ketone (3.5g) was further added thereto, followed by stirring for 3 hours. After cooling to 60 ℃ isopropanol (83g) was added.

Then, 155g of the polymerization solution (solid content concentration: 40% by mass) was weighed, and methyl ethyl ketone (7g), isopropyl alcohol (23.1g), 20% maleic anhydride aqueous solution (0.6g), and 2 mol/L NaOH aqueous solution (20g) were added to the solution, and the temperature in the reaction vessel was raised to 70 ℃. Subsequently, 190g of distilled water was added dropwise to disperse the water. Then, after the reaction vessel was kept at an internal temperature of 85 ℃ under atmospheric pressure for 1 hour, the pressure in the reaction vessel was reduced, and isopropanol and methyl ethyl ketone were distilled off to obtain an aqueous dispersion of resin particles P1 (solid content concentration 30 mass%). The resin particles P1 had a Tg of 150 ℃ and a weight-average molecular weight of 50,000.

(Synthesis of dispersant D1)

A dispersant D1 (resin dispersant) which is one of the components in the ink was synthesized. The details are shown below.

Dipropylene glycol of the same mass as the total amount of the monomers described later was added to a three-necked flask equipped with a stirrer and a cooling tube, and heated to 85 ℃ under a nitrogen atmosphere.

A solution I obtained by mixing 9.1 molar equivalents of stearyl methacrylate, 34.0 molar equivalents of benzyl methacrylate, 31.9 molar equivalents of hydroxyethyl methacrylate, 25.0 molar equivalents of methacrylic acid, and 0.8 molar equivalents of 2-mercaptopropionic acid, and a solution II obtained by dissolving 1 mass% of t-butyl peroxy-2-ethylhexanoate (Perbutyl O manufactured by NOF CORPORATION) based on the total mass of the monomers in 20 mass% of dipropylene glycol based on the total mass of the monomers were prepared, respectively. To the three-necked flask, the solution I was added dropwise over 4 hours, and the solution II was added dropwise over 5 hours.

After the completion of the dropwise addition, the reaction mixture was further reacted for 2 hours, and then heated to 95 ℃ and stirred for 3 hours to allow all the unreacted monomers to react. By nuclear magnetic resonance method (¹H-NMR method) confirmed the disappearance of the monomer.

The resulting reaction solution was heated to 70 ℃, 20.0 molar equivalents of dimethylaminoethanol (dimethylethanolamine) was added as an amine compound, and then propylene glycol was added thereto and stirred to obtain a 30 mass% solution of dispersant D1.

By passing¹H-NMR confirmed the constituent components of the obtained polymer. The weight average molecular weight (Mw) was 22,000 as determined by GPC.

The mass ratio of each structural unit in dispersant D1 was 20/39/27/14, which was structural unit derived from stearyl methacrylate/structural unit derived from benzyl methacrylate/structural unit derived from hydroxyethyl methacrylate/structural unit derived from methacrylic acid. Wherein the mass ratio is a value not including dimethylaminoethanol.

(preparation of pigment Dispersion)

A pigment dispersion was prepared as follows using Ready mill model LSG-4U-08 (manufactured by Aimex Co., Ltd.).

Into a zirconia container were charged titanium dioxide particles (Ishihara SANGYO KAISHA, LTD., manufactured by PF-690, average primary particle diameter 210nm), a 30 mass% solution of the above dispersant D1, and ultrapure water as a white pigment. Further, 0.5 mm. phi. zirconia beads (Traceram beads manufactured by TORAY) (titanium dioxide particles: beads 1.125:1 (mass ratio)) were added thereto, and the mixture was gently mixed with a spatula.

The zirconia container was placed in a ball mill and dispersed at 1000rpm for 5 hours. After the end of the dispersion, the beads were removed by filtration through a filter cloth, to obtain a pigment dispersion as an aqueous pigment dispersion having a pigment concentration of 45 mass% and a concentration of dispersant D1 of 1.35 mass%.

(preparation of ink)

An aqueous dispersion (solid content concentration: 30% by mass) of the resin particles P1, a 30% by mass solution of the dispersant D1, and components other than "white pigment, dispersant D1, and resin particles P1" in the following composition were mixed to prepare an ink having the following composition.

In table 1, the total of the dispersant D1 and the resin particles P1 is referred to as "the entire resin".

Composition of the ink

White pigment (titanium dioxide particles, average primary particle diameter 210nm)

… 10 mass%

Dispersant D1 (solid content in 30% by mass solution of dispersant D1)

… 0.3.3% by mass

Resin particles P1 (solid content in aqueous dispersion of resin particles P1)

… 4 mass%

Urea [ Compound A ]

… 1 mass%

Propylene glycol (manufactured by FUJIFILM Wako Pure Chemical Corporation) [ water-soluble solvent ]

… 20 mass%

SOLSPERSE (registered trademark) 43000 (manufactured by Noveon corporation) [ dispersion stabilizer ]

… 0.100.100% by mass

Polyvinylpyrrolidone K15(Tokyo Chemical Industry co., ltd.) [ water-soluble polymer compound ]

… 0.100.100% by mass

Surfynol 104(Nissin Chemical Co., Ltd.) [ defoaming agent ]

… 1.00.00% by mass

SNOWTEX (registered trademark) XS (manufactured by Nissan Chemical Corporation) [ colloidal silica ]

… 0.060.060 mass%

BYK (registered trademark) -024 (manufactured by BYK Japan KK) [ antifoaming agent ]

… 0.01.01% by mass

Water: the balance of the whole becomes 100 mass%

The pH of the obtained ink was measured at 25 ℃ using a pH meter (MM-60R type manufactured by DKK-TOA CORPORATION), and the results were shown in Table 1.

< preparation of treatment liquid >

A treatment liquid having the following composition was prepared.

Composition of the treatment liquid

Eastek (registered trademark) 1100 (manufactured by Eastman Chemical company) [ polyester resin particles ]

… 10 mass%

Malonic acid (manufactured by FUJIFILM Wako Pure Chemical Corporation) [ flocculant ]

… 5 mass%

… 10 mass%

Water: the balance of the whole becomes 100 mass%

The pH of the resulting treatment liquid was measured at 25 ℃ using a pH meter (MM-60R model manufactured by DKK-TOA CORPORATION), and the results were shown in Table 1.

< image recording >

Image recording was performed as follows using an ink set including the ink and the treatment liquid.

As an inkjet head, a GELJET (registered trademark) GX5000 printer head manufactured by RICOH Company, ltd. The printer head is a line head in which 96 nozzles are arranged.

The printer head is fixed to an ink jet recording apparatus having the same structure as the ink jet recording apparatus shown in fig. 1.

In this case, the arrangement was such that the direction in which the 96 nozzles were arranged was inclined by 75.7 ° with respect to the direction perpendicular to the moving direction of the stage of the ink jet apparatus on the same plane.

The ink discharge surface of the line head is provided with a liquid repellent film containing a fluorine compound. The liquid-repellent film comprising a fluorine compound is C₈F₁₇C₂H₄SiCl₃The monomolecular film (SAM film) of (1).

A polyethylene terephthalate (PET) substrate (FE2001, 12 μm thick, manufactured by FUTAMURA CHEMICAL co., ltd.) was prepared as an impermeable substrate, and the following treatment liquid application step, ink application step, and drying step were performed in this order using this PET substrate.

(treatment liquid applying step)

The PET substrate was fixed to a table of an inkjet recording apparatus, and then the treatment liquid was applied to the PET substrate using a wire bar while moving the table to which the PET substrate was fixed in a linear direction at a constant speed of 500 mm/sec. The applied amount of the treatment liquid was set to 1.4g/m ²。

At the position where the application of the treatment liquid was completed, the drying of the treatment liquid was started under the condition of 50 ℃ using a dryer 1.5 seconds after the application of the treatment liquid to the position was completed, and the drying was completed 3.5 seconds after the application of the treatment liquid was completed. The drying time at this time was 2 seconds.

(image recording step)

The ink was ejected from the printer head in a line pattern on the surface of the PET substrate to which the treatment liquid was applied while moving the PET substrate on which the drying of the treatment liquid was completed at a constant table speed of 50 mm/sec, thereby forming a solid film. The amount of ink applied was set to 11g/m²。

The ink ejection is started within 2 seconds from the end of the drying of the treatment liquid.

The ink discharge conditions were set to 4.5pL of ink droplet volume, 24kHz of discharge frequency, and 1200dpi × 1200dpi (dot per inch) of resolution.

Further, as the ink, an ink degassed by a degassing filter and adjusted to 30 ℃ was used.

Next, the ink applied to the surface of the PET substrate to which the treatment liquid was applied was dried at 70 ℃ for 10 seconds, whereby an image (solid image in detail) was obtained.

Thus, an image recorded matter including a PET substrate and an image disposed on the PET substrate was obtained.

< evaluation >

The image recorded matter obtained in the above was subjected to the following evaluation.

The results are shown in Table 1.

(concealment)

The solid image hiding property of the image recorded matter was evaluated as follows.

Unlike the image recorded matter, black character images (4 in number) of each size of 2pt (dot), 4pt, 6pt and 8pt were recorded on the PET substrate using a commercially available black inkjet ink, and a substrate with a black character image was obtained. The 4 black character images are each set to the black character image shown in fig. 2.

The image-recorded material and the base material with the black character image were superimposed in a direction in which the non-image-recorded surfaces (surfaces on which no image was recorded) of the base material were in contact with each other, to prepare a laminate. The obtained laminate was shielded by a 30W fluorescent lamp so that the solid image was directed toward the evaluator, and whether or not the details of each black character image could be visually recognized was confirmed by the solid image, and the concealment of the solid image was evaluated according to the following evaluation criteria. In this case, the distance between the observer's eyes and the laminate was 20cm, and the distance from the laminate to the fluorescent lamp was 2 m.

Among the evaluation criteria described below, the grade of the solid image having the most excellent concealment was "5".

Evaluation criteria for the concealment of solid images-

5: details cannot be visually recognized for black character images of 2pt, 4pt, 6pt, and 8 pt.

4: while the details of the 8pt black character image can be visually recognized, the details of the 2pt, 4pt, and 6pt black character images cannot be visually recognized.

3: while the details of the black character images of 6pt and 8pt can be visually recognized, the details of the black character images of 2pt and 4pt cannot be visually recognized.

2: while the details of the black character images of 4pt, 6pt, and 8pt can be visually recognized, the details of the black character images of 2pt cannot be visually recognized.

1: the details of the black character images of 2pt, 4pt, 6pt, and 8pt can be visually recognized.

(Adhesivity)

The images in the image recorded matter were subjected to a hundred-grid test in accordance with ISO2409 (cross-cut method), and the adhesion of the images was evaluated in accordance with the following evaluation criteria.

In the following evaluation criteria, the most excellent adhesion of the image was rated as "5".

In the one-hundred-grid test, 25 square grids of 1mm square are formed with the cutting interval set to 1 mm.

In the evaluation criteria below, the ratio (%) of lattice peeling is a value determined by the following formula. The total number of lattices in the following formula was 25.

The ratio (%) of lattice peeling [ ((number of lattices causing peeling)/(total number of lattices) ]) x 100

Evaluation criteria for adhesion of images over time-

5: the rate (%) of grid peeling is 0% to 5%.

4: the rate (%) of grid peeling exceeded 5% and was 15% or less.

3: the rate (%) of grid peeling exceeded 15% and was 35% or less.

2: the rate (%) of grid peeling exceeded 35% and was 65% or less.

1: the rate (%) of lattice peeling exceeded 65%.

(void ratio of image)

The porosity of the image in the image recorded matter was measured by the above-described method.

The SEM image used for calculation of the porosity of the image was obtained using a Thermo Fisher Scientific k.k. manufacturing Helios 400S FIB-SEM complex machine.

[ example 2 to example 28, comparative example 1 to comparative example 3 ]

The same operations as in example 1 were performed except that the pH of the ink, the amount of the compound a in the ink, the amount of the resin (i.e., the resin dispersant and the resin particles) in the ink, the Tg of the resin particles in the ink, the pH of the treatment liquid, the kind of the coagulant in the treatment liquid, and the amount of the treatment liquid added were changed as shown in table 1.

The results are shown in Table 1.

In the inks (pH7.5 or pH6.8) of examples 2, 4 and 5, the pH of the ink was adjusted to the values shown in table 1 by replacing a part of the water in the ink (pH8.5) of example 1 with hydrochloric acid as a pH adjuster. In these inks, the content of the pH adjuster is less than 1% by mass relative to the total amount of the ink.

In the treatment liquids of examples 14 to 16, the pH of the treatment liquid was adjusted to 4.0 by replacing a part of the water in the treatment liquid of example 1 with hydrochloric acid as a pH adjuster. In these treatment liquids, the content of the pH adjuster is less than 1 mass% with respect to the total amount of the treatment liquids.

In examples 12 and 13, the resin particles P1(Tg of 150 ℃) in the ink of example 1 were changed to the following resin particles P2(Tg of 60 ℃) and the following resin particles P3(Tg of 0 ℃).

Synthesis of resin particles P2(Tg 60 ℃ C.) in the ink in example 12

A three-necked flask equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen inlet was charged with methyl ethyl ketone (281g), and the temperature was raised to 85 ℃. While maintaining the reflux state, a mixed solution of methyl methacrylate (120g), isobornyl methacrylate (73g), methacrylic acid (30g), dodecyl methacrylate (75g), methyl ethyl ketone (66g) and "V-601" (manufactured by FUJIFILM Wako Pure Chemical Corporation) (0.66g) was uniformly dropped so that the dropping was completed within 3 hours. After completion of the dropwise addition, stirring was carried out for 1 hour, and (1) a solution composed of "V-601" (0.66g) and methyl ethyl ketone (3.5g) was added and stirred for 2 hours. Subsequently, the step (1) was repeated 4 times, and a solution of "V-601" (0.66g) and methyl ethyl ketone (3.5g) was further added thereto, followed by stirring for 3 hours. After cooling to 60 ℃ isopropanol (83g) was added.

Then, 155g of the polymerization solution (solid content concentration: 40% by mass) was weighed, and methyl ethyl ketone (7g), isopropyl alcohol (23.1g), 20% maleic anhydride aqueous solution (0.6g), and 2 mol/L NaOH aqueous solution (20g) were added to the solution, and the temperature in the reaction vessel was raised to 70 ℃. Subsequently, 190g of distilled water was added dropwise to disperse the water. Then, after the reaction vessel was kept at an internal temperature of 85 ℃ under atmospheric pressure for 1 hour, the pressure in the reaction vessel was reduced, and isopropanol and methyl ethyl ketone were distilled off to obtain an aqueous dispersion of resin particles P2 (solid content concentration 30 mass%). The resin particles P2 had a Tg of 60 ℃ and a weight-average molecular weight of 65,000.

Preparation of resin particles P3(Tg ═ 0 ℃) in the ink in example 13

A three-necked flask equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen inlet was charged with methyl ethyl ketone (281g), and the temperature was raised to 85 ℃. While maintaining the reflux state, a mixed solution of methyl methacrylate (60g), isobornyl methacrylate (43g), methacrylic acid (30g), dodecyl methacrylate (165g), methyl ethyl ketone (66g) and "V-601" (manufactured by FUJIFILM Wako Pure Chemical Corporation) (0.66g) was uniformly dropped so that the dropping was completed within 3 hours. After completion of the dropwise addition, stirring was carried out for 1 hour, and (1) a solution composed of "V-601" (0.66g) and methyl ethyl ketone (3.5g) was added and stirred for 2 hours. Subsequently, the step (1) was repeated 4 times, and a solution of "V-601" (0.66g) and methyl ethyl ketone (3.5g) was further added thereto, followed by stirring for 3 hours. After cooling to 60 ℃ isopropanol (83g) was added.

Then, 155g of the polymerization solution (solid content concentration: 40% by mass) was weighed, and methyl ethyl ketone (7g), isopropyl alcohol (23.1g), 20% maleic anhydride aqueous solution (0.6g), and 2 mol/L NaOH aqueous solution (20g) were added to the solution, and the temperature in the reaction vessel was raised to 70 ℃. Subsequently, 190g of distilled water was added dropwise to disperse the water. Then, after the reaction vessel was kept at an internal temperature of 85 ℃ under atmospheric pressure for 1 hour, the pressure in the reaction vessel was reduced, and isopropanol and methyl ethyl ketone were distilled off to obtain an aqueous dispersion of resin particles P3 (solid content concentration 30 mass%). The resin particles P3 had a Tg of 0 ℃ and a weight-average molecular weight of 70,000.

[ Table 1]

Description of Table 1

The amount of the component in the ink is the content (mass%) of the entire ink, and the amount of the component in the treatment liquid is the content (mass%) of the entire treatment liquid.

The "resin component" refers to a resin component in which the resin dispersant and the resin particles are combined.

The white pigment is titanium dioxide particles.

The compound A is urea.

The white pigment/compound a is the ratio of the contained mass of the white pigment to the contained mass of the compound a.

The resin mass/compound a is a ratio of the content mass of the resin mass (i.e., the resin dispersant and the resin particles) to the content mass of the compound a.

The term (white pigment + resin whole)/compound a is a ratio of the total content mass of the white pigment and the resin whole (i.e., the resin dispersant and the resin particles) to the content mass of the compound a.

Regarding the Y/X ratio, the amount of the treatment liquid applied per unit area in the treatment liquid applying step is Xg/m²The ink supply per unit area in the image recording step is Yg/m²The ratio of Y to X in the above case.

In table 1, specific pH adjusters in the treatment liquid are shown below.

Malonic acid manufactured by FUJIFILM Wako Pure Chemical Corporation

·CaCl₂… CaCl manufactured by FUJIFILM Wako Pure Chemical Corporation₂

Titanium lactate ("Orgatix TC-310" manufactured by Matsumoto Fine Chemical co., ltd.)

Cationic Polymer 1 … Poly-2-hydroxypropyldimethylammonium chloride ("cation Master PD-7" manufactured by Yokkaichi Chemical Company Limited)

As shown in table 1, in each example using an ink set having: a treatment liquid having a pH of 4.5 or less or 9.5 or more; and an ink containing a compound A which generates a gas in an environment having a pH of 4.5 or less or 9.5 or more, a resin, water and a white pigment, wherein the pH is more than 4.5 and less than 9.5, and the ratio of the white pigment/the compound A (i.e., the ratio of the content mass of the white pigment to the content mass of the compound A) in the ink is 1 or more and 160 or less.

In contrast to these examples, in each of comparative example 1 in which the pH of the treatment liquid was more than 4.5 and less than 9.5 and comparative example 2 in which the white pigment/compound a was 160 or more, the concealing property of the image was lowered. The reason for this is considered to be that the void ratio in the image is reduced because no gas based on compound a is generated.

In comparative example 3 in which the white pigment/compound a was less than 1, the adhesion of the image was reduced. The reason for this is considered to be that the void ratio in the image is too large.

From the results of examples 1 to 5, it is understood that when the absolute value of the difference between the pH of the treatment liquid and the pH of the ink is 3 or more (examples 1 to 4), the concealing property of the image is further improved.

From the results of examples 6 and 8, it is understood that when the total resin/compound a in the ink is 0.3 or more (example 8), the adhesion of the image is further improved.

From the results of examples 7 and 9, it is understood that when the total resin/compound a in the ink is 100 or less (example 9), the concealing property of the image is further improved.

From the results of example 12 and example 13, it is understood that when the glass transition temperature (Tg) of the resin particles is 40 ℃ or higher (example 12), the adhesion of the image is further improved.

From the results of examples 1 and 4 and examples 14 to 16, it is understood that when the treatment liquid contains an organic acid as a coagulant (example 1), the concealing property of the image is further improved.

Description of the symbols

11-supply section, 12-treatment liquid applying section, 13-treatment liquid drying region, 14-ink ejecting section, 15-ink drying region, 16-accumulating section, 20-anilox roller, 22-coating roller, 24-opposed roller, 30W, 30K, 30C, 30M, 30Y, 30A-head for ink ejection, 41, 42, 43, 44, 45, 46-conveying roller.

Claims

1. An ink set comprising:

a treatment liquid having a pH of 4.5 or less or 9.5 or more; and

2. The ink set according to claim 1, wherein an absolute value of a difference between the pH of the treatment liquid and the pH of the ink is 3 or more.

3. The ink set according to claim 1 or 2, wherein a ratio of a content mass of the resin in the ink to a content mass of the compound a is 0.3 or more and 100 or less.

4. The ink set according to any one of claims 1 to 3, wherein a ratio of a total contained mass of the white pigment and the resin in the ink to a contained mass of the compound A is 3 or more and 250 or less.

5. An ink set according to any one of claims 1 to 4, wherein the compound A is urea.

6. The ink set according to any one of claims 1 to 5, wherein a content of the white pigment in the ink is 5 to 20% by mass with respect to a total amount of the ink.

7. The ink set according to any one of claims 1 to 6, wherein the white pigment contains titanium dioxide particles.

8. The ink set according to any one of claims 1 to 7, wherein the ink is a white ink.

9. The ink set according to any one of claims 1 to 8, wherein the content of the resin is 1 to 10 mass% with respect to the total amount of the ink,

10. The ink set according to any one of claims 1 to 9, wherein the resin contains resin particles.

11. The ink set according to claim 10, wherein the glass transition temperature of the resin particles is 40 ℃ or higher.

12. An ink set according to any one of claims 1 to 11, wherein the ink is an inkjet ink.

13. The ink set according to any one of claims 1 to 12, wherein the treatment liquid contains at least one coagulant selected from an organic acid, a polyvalent metal compound, a metal complex, and a water-soluble cationic polymer.

14. The ink set according to any one of claims 1 to 13, which is used for image recording to an impermeable substrate.

15. An image recording method using the ink set according to any one of claims 1 to 14, the image recording method having the steps of:

a step of applying the treatment liquid to an impermeable base material; and

and a step of applying the ink to the surface of the non-permeable substrate to which the treatment liquid is applied, thereby recording an image.

16. The image recording method according to claim 15, wherein an amount of the treatment liquid applied per unit area in the step of applying the treatment liquid is Xg/m²The amount of the ink applied per unit area in the step of recording the image is Yg/m²In the case of (2), the Y/X ratio is 3 to 25 inclusive.

17. An image recorded matter, comprising:

An impermeable substrate; and

the porosity in the image is 1% or more and 30% or less.